- Montmorillonite-mediated hetero-Diels-Alder reaction of alkenes and o-quinomethanes generated in situ by dehydration of o-hydroxybenzyl alcohols
-
The intermolecular hetero-Diels-Alder reaction of in situ-generated o-quinomethanes and unactivated alkenes has been accomplished through a wet montmorillonite catalyst in a LiClO4-MeNO2 solution to give good yields of varied chromane skeletons.
- Chiba, Kazuhiro,Hirano, Tetsuya,Kitano, Yoshikazu,Tada, Masahiro
-
-
Read Online
- One pot tandem dual CC and CO bond reductions in the β-alkylation of secondary alcohols with primary alcohols by ruthenium complexes of amido and picolyl functionalized N-heterocyclic carbenes
-
Two different classes of ruthenium complexes, namely, [1-mesityl-3-(2,6-Me2-phenylacetamido)-imidazol-2-ylidene]Ru(p-cymene)Cl (1c) and {[1-(pyridin-2-ylmethyl)-3-(2,6-Me2-phenyl)-imidazol-2-ylidene]Ru(p-cymene)Cl}Cl (2c), successfully catalyzed the one-pot tandem alcohol-alcohol coupling reactions of a variety of secondary and primary alcohols, in moderate to good yields of ca. 63-89%. The mechanistic investigation performed on two representative catalytic substrates, 1-phenylethanol and benzyl alcohol using the neutral ruthenium (1c) complex showed that the catalysis proceeded via a partially reduced CC hydrogenated carbonyl species, [PhCOCH2CH2Ph] (3′), to the fully reduced CO and CC hydrogenated secondary alcohol, [PhCH(OH)CH2CH2Ph] (3). Furthermore, the time dependent study showed that the major product of the catalysis modulated between (3′) and (3) during the catalysis run performed over an extended period of 120 hours. Finally, the practical utility of the alcohol-alcohol coupling reaction was demonstrated by preparing five different flavan derivatives (13-17) related to various bioactive flavonoid natural products, in a one-pot tandem fashion.
- Dey, Shreyata,Ghosh, Prasenjit,Prakasham, A. P.,Ta, Sabyasachi
-
p. 15640 - 15654
(2021/11/30)
-
- Boron insertion into alkyl ether bonds via zinc/nickel tandem catalysis
-
Mild methods to cleave the carbon-oxygen (C?O) bond in alkyl ethers could simplify chemical syntheses through the elaboration of these robust, readily available precursors. Here we report that dibromoboranes react with alkyl ethers in the presence of a nickel catalyst and zinc reductant to insert boron into the C?O bond. Subsequent reactivity can effect oxygen-to-nitrogen substitution or one-carbon homologation of cyclic ethers and more broadly streamline preparation of bioactive compounds. Mechanistic studies reveal a cleavage-then-rebound pathway via zinc/nickel tandem catalysis.
- Lyu, Hairong,Kevlishvili, Ilia,Yu, Xuan,Liu, Peng,Dong, Guangbin
-
-
- Axially Chiral 1,1'-Binaphthyl-2-Carboxylic Acid (BINA-Cox) as Ligands for Titanium-Catalyzed Asymmetric Hydroalkoxylation
-
Axially chiral, enantiopure 1,1'-binaphthyl-2-carboxylic acids (BINA-Cox) have recently been introduced as chiral ligands for transition metal catalysis. Together with equimolar, co-catalytic amounts of Ti(OiPr)4 and water they form an in situ catalyst that performs the asymmetric catalytic hydroalkoxylation of 2-allylphenols to 2-methylcoumarans at high temperature (240 °C, microwave heating). The synthesis of reference ligand 2'-MeO-BINA-Cox (L1) has been optimized and performed at molar scale. Synthetic routes have been developed to access a variety of substituted BINA-Cox ligands (>30 examples), which have been tested for ligand effects on the reference asymmetric cyclization of 2-allylphenol. The substrate range of asymmetric catalytic hydroalkoxylation has been explored through systematic substrate structure variations to define scope and limitations of the titanium-catalyzed process. The new substrates 2-(1-vinylcycloalkyl)phenols (1j, 1k), 2-(2-vinylphenyl)propan-2-ol (1t), and 2'-vinyl-[1,1'-biphenyl]-2-ol (1u) are shown to undergo asymmetric catalytic cyclization to benzodihydrofurans and benzo[c]chromene, respectively.
- Blazejak, Max,Helmbrecht, Sebastian L.,Hintermann, Lukas,Schlüter, Johannes
-
supporting information
(2020/04/15)
-
- One-Pot Synthesis of O-Heterocycles or Aryl Ketones Using an InCl3/Et3SiH System by Switching the Solvent
-
An efficient one-pot synthesis of O-heterocycles or aryl ketones has been achieved using Et3SiH in the presence of InCl3 via a sequential ionic hydrogenation reaction by switching the solvent. This methodology can be used to construct C-O bonds and to prepare conjugate reduction products, including chromans, tetrahydrofurans, tetrahydropyrans, dihydroisobenzofurans, dihydrochalcones, and 1,4-diones in a facile manner. In addition, a novel plausible mechanism involving a conjugate reduction and a tandem reductive cyclization was verified by experimental investigations.
- Jia, Wenqiang,Xi, Qiumu,Liu, Tianqi,Yang, Minjian,Chen, Yonghui,Yin, Dali,Wang, Xiaojian
-
p. 5141 - 5149
(2019/05/10)
-
- Manganese-Catalyzed β-Alkylation of Secondary Alcohols with Primary Alcohols under Phosphine-Free Conditions
-
Manganese(I) complexes bearing a pyridyl-supported pyrazolyl-imidazolyl ligand efficiently catalyzed the direct β-alkylation of secondary alcohols with primary alcohols under phosphine-free conditions. The β-alkylated secondary alcohols were obtained in moderate to good yields with water formed as the byproduct through a borrowing hydrogen pathway. β-Alkylation of cholesterols was also effectively achieved. The present protocol provides a concise atom-economical method for C-C bond formation from primary and secondary alcohols.
- Liu, Tingting,Wang, Liandi,Wu, Kaikai,Yu, Zhengkun
-
p. 7201 - 7207
(2018/07/21)
-
- Regioselective Domino Synthesis of 2-Alkylflavans via Hidden Br?nsted Acid Catalysis
-
A range of alkyl-substituted flavans, which are important structural elements in natural products and pharmaceutical molecules, were prepared by successive hidden Br?nsted acid catalyzed domino reaction, intermolecular hydroarylation, and intramolecular hydroalkoxylation. 1,1-Disubstituted allenes were activated under mild acidic AgOTf/t-BuCl condition to initiate the regioselective Friedel-Crafts reaction with phenol derivatives, and the consecutive reaction triggered by the 6 -endo cyclization led to the formation of a new type of 2-alkylflavan. Mechanistic study of the reaction intermediates and control experiments support the catalytic pathway and advantage of hidden Bronsted acid catalysis.
- Jin, Ha Jeong,Kim, Jae Hyung,Kang, Eun Joo
-
supporting information
p. 3137 - 3144
(2017/07/12)
-
- Tandem Cross Coupling Reaction of Alcohols for Sustainable Synthesis of β-Alkylated Secondary Alcohols and Flavan Derivatives
-
A Ru(II) NHC complex (loading down to 0.001 mol%) catalyzed cross coupling of a broad range of aromatic, aliphatic and heterocyclic alcohols is reported. This protocol also functioned efficiently under solvent-free conditions. Remarkably, this catalytic system disclosed so far the highest TON of 288000 for the cross coupling of alcohols. Notably, this methodology was successfully applied for the one-pot synthesis of a range of flavan derivatives. A detailed DFT studies and kinetic experiments were performed to understand the reaction mechanism as well as the high reactivity of this catalytic system. (Figure presented.).
- Shee, Sujan,Paul, Bhaskar,Panja, Dibyajyoti,Roy, Bivas Chandra,Chakrabarti, Kaushik,Ganguli, Kasturi,Das, Ayan,Das, Gourab Kanti,Kundu, Sabuj
-
supporting information
p. 3888 - 3893
(2017/10/07)
-
- A Modular Synthesis of 2-Alkyl- and 2-Arylchromans via a Three-Step Sequence
-
A convergent three-step method for the synthesis of 2-substituted chromans is described. These results have been accomplished via the Heck coupling of readily accessible allylic alcohols and 2-iodophenols, followed by reduction and Mitsunobu cyclization. The utility and generality of this method is demonstrated through the synthesis of a series of 2-aryl-, 2-heteroaryl- and 2-alkylchromans, as well as an azachroman derivative. The asymmetric version of this approach via a Noyori-catalyzed ketone reduction and subsequent cyclization is likewise highlighted.
- Orr, Robert K.,Campeau, Louis-Charles,Chobanian, Harry R.,McCabe Dunn, Jamie M.,Pio, Barbara,Plummer, Christopher W.,Nolting, Andrew,Ruck, Rebecca T.
-
p. 657 - 666
(2017/01/28)
-
- Tosylhydrazine mediated conjugate reduction and sequential reductive coupling cyclization: Synthesis of 2-arylchromans
-
Tosylhydrazine mediated conjugate reduction of 2-hydroxyl chalcones and sequential reductive coupling cyclization is described. This is an unprecedented protocol and an extremely efficient method for a one-pot domino synthesis of 2-arylchromans in good to excellent yields from commercially available, cheap starting materials. More importantly, the two-step reactions can be easily controlled to afford dihydrochalcones or 2-arylchromans by the mole amounts of tosylhydrazine. Furthermore, the operational simplicity of the process and the high functional group tolerance are remarkable.
- Shang, Xuyang,Zhou, Xiaomeng,Zhang, Wei,Wan, Changfeng,Chen, Junmin
-
p. 8187 - 8193
(2015/12/30)
-
- Synthesis of 2-aryl-substituted chromans by intramolecular C-O bond formation
-
A synthetic route for the preparation of 2-aryl-substituted chromans from commercially available starting materials and utilizing either a palladium- or copper-catalyzed intramolecular cyclization of aryl bromides is described. Chromans with stereocontrol at C-2 can thus be obtained via a palladium-catalyzed asymmetric allylic etherification procedure utilizing a chiral indole-phosphine oxazoline (IndPHOX) ligand. Georg Thieme Verlag Stuttgart · New York.
- Wang, Yu,Franzén, Robert
-
p. 925 - 929
(2012/06/15)
-
- Intramolecular hydroalkoxylation in Bronsted acidic ionic liquids and its application to the synthesis of (±)-centrolobine
-
The SO3H-tethered imidazolium and triazolium salts, nonvolatile and recyclable Bronsted acidic ionic liquids, efficiently mediate intramolecular hydroalkoxylations of alkenyl alcohols. They have been successfully employed in the synthesis of (±)-centrolobine.
- Jeong, Yunkyung,Kim, Do-Young,Choi, Yunsil,Ryu, Jae-Sang
-
supporting information; experimental part
p. 374 - 378
(2011/02/28)
-
- An efficient synthesis of flavans from salicylaldehyde and acetophenone derivatives
-
An efficient total synthesis of flavans from the reactions of salicylaldehyde and acetophenone derivatives is reported. The synthesis involves preparation of chalcones through an aldol reaction followed by reduction of both the double bond and the ketone using NaBH4 and an acetic acid mediated cyclization. Methoxy groups on the aromatic rings did not affect significantly the yields of the procedure.
- Mazimba, Ofentse,Masesane, Ishmael B.,Majinda, Runner R.
-
p. 6716 - 6718
(2012/01/02)
-
- Pt(IV)-catalyzed generation and [4+2]-cycloaddition reactions of o-quinone methides
-
Novel intermolecular and intramolecular generations of ortho-quinone methides and their formal [4+2]-cycloaddition reactions with olefins catalyzed by PtCl4 and AuCl3 under mild conditions have been developed. Good to excellent yields (up to 99%) and diastereoselectivity (up to >99:1) of the chromans were obtained. PtCl4 was found to be effective and compatible with various functional groups present in the substrates. A mechanism accounting for its catalytic cycle is proposed and discussed.
- Radomkit, Suttipol,Sarnpitak, Pakornwit,Tummatorn, Jumreang,Batsomboon, Paratchata,Ruchirawat, Somsak,Ploypradith, Poonsakdi
-
p. 3904 - 3914
(2011/06/22)
-
- Generation of ortho-quinone methides by p-TsOH on silica and their hetero-Diels-Alder reactions with styrenes
-
(Chemical Equation Presented) 2-Arylchromans were readily prepared from the hetero-Diels-Alder reactions of styrenes with the ortho-quinone methides (o-QMs) which, in turn, were generated by treating the MOM-protected benzylacetate derivatives with p-TsOH immobilized on silica (PTS-Si) in toluene under mild conditions (0°C to rt). The corresponding chromans were obtained in moderate to excellent yields (42-97%) and in moderate to excellent diastereoselectivity (up to >99:1).
- Batsomboon, Paratchata,Phakhodee, Wong,Ruchirawat, Somsak,Ploypradith, Poonsakdi
-
experimental part
p. 4009 - 4012
(2009/10/14)
-
- Reduction of some flavanones and E-3-benzylideneflavanones under modified Clemmensen reduction condition
-
A mild and efficient method for reduction of flavanones and E-3-benzylideneflavanones has been developed by using modified Clemmensen reduction condition [Zn(Hg), CH3COOH, EtOH, reflux, 1.5 h]. Flavanones gave flavans and E-3-benzylideneflavanones gave 3-benzylflavans and 3-benzylflav-3-enes.
- Deya, Sankar P.,Dey, Dilip K.,Dhara, Mrinal G.,Mallik, Asok K.
-
body text
p. 717 - 720
(2009/12/05)
-
- Generation and application of o-Quinone methides bearing various substituents on the benzene ring
-
o-Quinone methides (o-QMs) are highly reactive, short-lived intermediates, which have potential synthetic applicability. However, few studies on the generation of o-QMs bearing an electron-withdrawing group have been reported. Herein we present a general method for the generation of o-QMs, particularly those substituted with an 0lectrophilic substituent, from new precursors, 4H-1,2-benzoxazines 2. We have also studied systematically the Diels-Alder reactions of o-QMs with various dienophiles, such as vinyl ethers, enamines and imines. The reactions provide a versatile route to substituted chromans, phenols and 3,4-dihydro-2H-benzo[e]-[1,3]oxazines (3,4-dihydro-1,3-benzoxazines). Furthermore, we applied the new method to the derivatization of some natural products.
- Sugimoto, Hiromichi,Nakamura, Satoshi,Ohwada, Tomohiko
-
p. 669 - 679
(2008/02/09)
-
- A new and efficient method for o-quinone methide intermediate generation: Application to the biomimetic synthesis of the benzopyran derived natural products (±)-lucidene and (±)-alboatrin
-
Lucidene and alboatrin are complex benzopyran derived natural products. A key step in their biogenesis may involve a hetero Diels-Alder cycloaddition between an o-quinone methide intermediate with a simple, or activated tri-substituted olefin. Experimental evidence is provided to support this hypothesis, with the biomimetic synthesis of both (±)-lucidene and (±)-alboatrin successfully achieved using a new and efficient method for o-quinone methide generation. The Royal Society of Chemistry 2005.
- Rodriguez, Raphael,Moses, John E.,Adlington, Robert M.,Baldwin, Jack E.
-
p. 3488 - 3495
(2007/10/03)
-
- A new and efficient method for o-quinone methide intermediate generation: Application to the biomimetic synthesis of (±)-Alboatrin
-
(Chemical Equation Presented) A new and efficient method for o-quinone methide intermediate generation from o-methyleneacetoxy-phenols has been developed and applied to the biomimetic synthesis of (±)-Alboatrin.
- Rodriguez, Raphael,Adlington, Robert M.,Moses, John E.,Cowley, Andrew,Baldwin, Jack E.
-
p. 3617 - 3619
(2007/10/03)
-
- 4H-1,2-benzoxazines with electron-withdrawing substituents on the benzene ring: Synthesis and application as potent intermediates for oxygen-functionalized aromatic compounds
-
A new general method for synthesizing functionalized 4H-1,2-benzoxazine derivatives is described. Although 4H-1,2-benzoxazine is one of the fundamental structure of the oxazine group, no general synthetic method for the heterocycle has been established. We found that 3-methoxycarbonyl-4H-1,2-benzoxazine was obtained in good yield when methyl 2-nitro-3-phenylpropionate was treated with an excess amount of trifluoromethanesulfonic acid. This methodology was also applicable for the synthesis of 4H-1,2-benzoxazine rings functionalized with various electron-withdrawing substituents on the benzene ring. Furthermore, we also show that the resulting 4H-1,2-benzoxazines can be used as precursors of functionalized o-quinone methides and multisubstituted phenols. This type of heterocycle can be a potent intermediate to oxygen-fuctionalized aromatic compounds. Copyright
- Nakamura, Satoshi,Uchiyama, Masanobu,Ohwada, Tomohiko
-
p. 5282 - 5283
(2007/10/03)
-
- Acaricidal activity of tonka bean extracts. Synthesis and structure-activity relationships of bioactive derivatives
-
The acaricidal effects of tonka bean, Dipterix odorata, extracts were investigated on Dermatophagoides pteronyssinus, the European house dust mite, and compared with benzyl benzoate as a standard acaricidal compound. A cyclohexane extract was the most effective, with an EC50 = 0.075 g/m2 after a 24 h period, as compared with benzyl benzoate (0.025 g/m2). Bioassay-guided fractionation of this extract led to the isolation of coumarin (1). Pharmacomodulation of this compound led us to test 20 analogues (2-21), which were either synthesized or purchased.
- Gleye, Christophe,Lewin, Guy,Laurens, Alain,Jullian, Jean-Christophe,Loiseau, Philippe,Bories, Christian,Hocquemiller, Reynald
-
p. 690 - 692
(2007/10/03)
-
- Reductive lithiation of cyclic benzofused ethers: A source of oxygen-functionalised organolithium compounds
-
The reaction of 2,3-dihydrobenzofuran (1) with lithium and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5%) in THF at 0°C for 1.5h, followed by addition of an electrophile [E+=H2O, tBuCHO, PhCH2CHO, Ph(CH2)2CHO, PhCHO, furfural, Me2CO, Et2CO, cyclopentanone, cyclohexanone, cyclooctanone, (-)-menthone] in THF at -78°C gives, after hydrolysis, compounds 3. Some diols 3 are easily transformed into 2-substituted chromans 6 under acidic reaction conditions. The reductive lithiation of chroman (7) at 20°C for 3h leads exclusively to the intermediate 8, which is formed through a dearylation process, and isomerises to the apparently more stable benzylic intermediate 9. The reaction of these intermediates with different electrophiles {E+=tBuCHO, PhCHO, furfural, Me2CO, [CH3(CH2)4]2CO, cyclopentanone, cyclohexanone, (-)-menthone, Ph2CO}, at -78°C in THF leads, after hydrolysis, to a mixture of regioisomers 10 and 11. The reaction of 2,3-benzofuran (12) with an excess of lithium and a catalytic amount of DTBB (5%) in THF at 0°C for 45min leads to dianionic intermediate 13 through a dealkylation process, which after hydrolysis gives 2-vinylphenol 14. In the case of 4H-chromene (15), reductive opening is performed at 20°C for 45min, a mixture of dearylation and dealkylation intermediates 16 and 17, respectively, is obtained (2:1 ratio) giving, after hydrolysis, 3-phenylpropanal (18) and 2-allylphenol (19).
- Yus, Miguel,Foubelo, Francisco,Ferrández, José V,Bachki, Abderrazak
-
p. 4907 - 4915
(2007/10/03)
-
- Photoreactions of trans-1-o-Hydroxyphenyl-2-phenylcyclopropane
-
The photochemistry of trans-1-o-hydroxyphenyl-2-phenylcyclopropane, trans-1, was studied under a variety of experimental conditions. Direct irradiation through quartz in cyclohexane gave rise mainly to ring-expanded products, 2-phenyl-3,4-dihydro-2H-benzopyran, 2, 2-benzyl-2,3-dihydrobenzofuran, 3, and 1-o-hydroxyphenylindan, 4. The major products, 2 and 3, are rationalized by intramolecular proton transfer. However, a significant fraction of 3 is formed via ring-opening to cinnamylphenol, 5. An additional product, o-(α-cyclohexylmethyl)phenol, 7, suggests fragmentation of trans-1 and (formal) insertion of o-hydroxyphenylcarbene into cyclohexane. Direct irradiation in methanol produced methanol adducts 8 and 9 instead of 2, 3,4, or 7. Finally, acetone-sensitized irradiation of trans-1 resulted in geometric isomerization to cis-1; this result can be rationalized via a biradical intermediate.
- Delgado, Julio,Espinos, Amparo,Jimenez, M. Consuelo,Miranda, Miguel A.,Roth, Heinz D.,Tormos, Rosa
-
p. 6541 - 6546
(2007/10/03)
-
- Organolithium reagents from alkyl phenyl ethers
-
The reaction of primary alkyl or vinyl phenyl ethers (1) as well as 2,3- dihydrobenzofuran (3) with an excess of lithium powder and a catalytic amount of DTBB (5 %) in THF at room temperature leads to the corresponding organolithium intermediates, which by treatment with different electrophiles [H2O, D2O, Me3SiCl, Bu(t)CHO, PhCHO, Me2CO, Et2CO, (CH2)4CO, (CH2)5CO, PhCOMe] and final hydrolysis affords the expected products 2 and 4.
- Bachki, Abderrazak,Foubelo, Francisco,Yus, Miguel
-
p. 7759 - 7762
(2007/10/03)
-
- Ground and excited-state intramolecular interactions in phenol-olefin bichromophoric compounds
-
The intramolecular OH ... π interactions of the phenolic and olefinic chromophores in o-propenyl and o-butenyl phenols 1a-d in the ground and excited states have been studied by (a) ab initio Hartree-Fock calculations using the 3-21G and 6-31G** basis sets, (b) FTIR spectral measurements in the gas phase, (c) fluorescence emission studies and (d) product studies. Such interactions appear to play a key role in the photochemical behaviour of the four compounds.
- Bosch-Montalva, M. Teresa,Domingo, Luis R.,Jimenez, M. Consuelo,Miranda, Miguel A.,Tormos, Rosa
-
p. 2175 - 2179
(2007/10/03)
-
- Photochemistry of allylphenol derivatives. Role of the phenolic and styrenic excited states in the behavior of bichromophoric cinnamylphenol
-
Irradiation of trans-2-cinnamylphenol (2a) in hexane, under argon, led to the cis isomer 2b, 2-benzyl-2,3-dihyrobenzofuran (3), and 2-phenyl-3,4- dihydro-2H-benzopyran (4). The presence of oxygen produced a marked decrease of the 2b yield, with a parallel enhancement of the pathway leading to 3 and 4. In benzene, the cyclization process was enhanced, together with the 3:4 ratio. The latter was less favored in the presence of photosensitizers with lower singlet energies, such as toluene, methyl benzoate, or p- dichlorobenzene. In the acetone-photosensitized reaction, a clean and efficient isomerization to 2b took place. These results, together with CNDO/S calculations, suggested involvement of the phenolic or the styrenic singlets in the cyclization to 3 or 4, respectively, and the styrenic triplet (partially quenched by oxygen) in the double bond isomerization to 2b. Addition of methanol to the benzene solutions of 2a partially quenched the photocyclization. By contrast, the formation of 4 was markedly enhanced in the presence of trimethylamine or triethylamine, which were also efficient fluorescence quenchers. The above observations evidenced a new route to product 4 involving electron transfer from the tertiary amine to excited trans-2-cinnamylphenol (2a). The key step in the photocyclization must be intramolecular excited-state proton transfer (ESPT) and appears to involve π-complexes of the type I, IIa, and IIb. Accordingly, direct irradiation of the o-acetyl derivative 9a resulted exclusively in isomerization to 9b, owing to chelation of the hydroxy group, which should prevent formation of the π- complexes and facilitate deactivation of the phenolic singlet, via intramolecular proton exchange.
- Jimenez,Marquez,Miranda,Tormos
-
p. 197 - 202
(2007/10/02)
-
- Reduction of flavanones by NaBH3CN in trifluoroacetic acid.
-
For our studies on the reduction of flavanones, we worked on flavanone itself and on some other derivatives, oxygenated on the B ring.Besides expected flavans and chalcanes, condensed compounds (dimers and trimers) are also obtained.Reaction begins with the reduction of carbonyl to methylene; all the other isolated products arise from the two possible and competitive reactions on the potential carbocation C-2 of the flavan system: a) reductive cleavage of heterocycle; b) electrophilic aromatic substitution.Reactivity of flavanones is correlated with substituents of B ring through their ?+ values. Key words: flavanones / sodium cyanoborhydride / trifluoroacetic acid / flavans / chalcanes / dimers
- Lewin, G.,Bert, M.,Dauguet, J. C.,Dolley, J.,Menez, P. Le,et al.
-
p. 939 - 944
(2007/10/02)
-
- Novel Generation of o-Quinone Methides on the Basis of Lewis Acid Catalyzed 1,4-Dethiolation of o-(1-(Alkylthio)alkyl)phenols
-
The treatment of o-(1-(alkylthio)alkyl)phenols with Lewis acid resulted in the formation of o-quinone methides by the novel 1,4-dethiolation process, which, being activated with Lewis acid, reacted in situ with various dienophiles in the manner of Diels-Alder reaction in high efficiency. o-Quinone allide, provided from o-(1-(alkylthio)allyl)phenol, also behaved as heterodienes.
- Inoue, Tsutomu,Inoue, Seiichi,Sato, Kikumasa
-
-
- Amino-substituted flavans useful as anti-viral agents
-
Novel compounds of formula (IID) STR1 wherein either both X and Y represent groups independently selected from amino and lower alkylamino, or one of X and Y represents a group selected from amino and lower alkylamino and the other of X and Y represents a hydrogen atom have been found to be active against rhinoviruses and other viruses. Processes for producing these compounds include reduction of flavanone derivatives or of flavenes. Alternatively, reductive cyclization of chalcones affords the compounds. These may also be prepared by condensation of o-(substituted methyl)phenols with styrene derivatives. Pharmaceutical formulations and methods for the administration of the compounds are described.
- -
-
-
- Reactions of Flav-2-enes and Flav-2-en-4-ones (Flavones)
-
Flav-2-enes, flavones, and 3-alkyl ethers of flavonols add alcohols and carboxylic acids in the presence of N-bromosuccinimide to give 2-alkoxy- and 2-acyloxy-3-bromoflavans which provide routes to cis-3-bromoflavans by reduction and to 3,4-diols by elimination and reaction with osmium tetraoxide.The 2-acyloxyflavans react with alcohols yielding 2-alkoxyflavans.Flavonols react with N-bromosuccinimide and alcohols to give bromine-free hemiacetals, the known 2,3-dialkoxy-3-hydroxyflavanones.
- Bird, T. Geoffrey C.,Brown, Ben R.,Stuart, Ian A.,Tyrrell, William R.
-
p. 1831 - 1846
(2007/10/02)
-