- Biarylphosphonite gold(I) complexes as superior catalysts for oxidative cyclization of propynyl arenes into indan-2-ones
-
Striking gold: A series of variously functionalized propynyl arenes was smoothly converted into indan-2-ones by a new gold(I)-catalyzed oxidative cyclization process. [LAu]NTf2 (Tf=trifluoromethanesulfonyl) is a superior catalyst both in terms of yield and kinetics for the present transformation. Copyright
- Henrion, Guilhem,Chavas, Thomas E. J.,Le Goff, Xavier,Gagosz, Fabien
-
supporting information
p. 6277 - 6282
(2013/07/11)
-
- Parallel synthesis of terminal alkynes using a ROMPgel-supported ethyl 1-diazo-2-oxopropylphosphonate
-
ROMPgel-supported ethyl 1-diazo-2-oxopropylphosphonate has been prepared, and the supported reagent has been effectively employed in the conversion of a variety of aldehydes into terminal alkynes under mild reaction conditions. The influence of cross-link structure, comonomers, and polymer structure on reaction efficiency has been examined.
- Barrett, Anthony G. M.,Hopkins, Brian T.,Love, Andrew C.,Tedeschi, Livio
-
p. 835 - 837
(2007/10/03)
-
- One post stereoselective synthesis of chiral αω-diynes from bromoallenes and organobis(heterocuprates)
-
Organobis(heterocuprates), 7 and 8, have been prepared reacting in situ 1,4-dilithiobutane and di-Grignard reagents, obtained from 1,4-dibromobutane and 1,4-dibromobenzene, respectively, with CuSPh and LiCuBr2. The cross-coupling reaction of these di-cuprate reagents with 3-alkyl and 3,3-dialkyl 1-bromo-1,2-dienes (1) provides a general method for selective synthesis of 1,9-decadiynes (5) and 1,4-bis(2-propynyl)benzenes (6), characterized by two identical chiral centres in the α position to the triple bonds. The high 1,3-anti stereoselectivity of the coupling process allows us to obtain enantiomerically enriched α,ω-diynes 5 and 6 starting from optically active allenic substrates 1.
- Caporusso, Anna Maria,Aronica, Laura Antonella,Geri, Roberto,Gori, Marco
-
p. 109 - 118
(2007/10/03)
-
- Silylformylation of chiral 1-alkynes, catalysed by solvated rhodium atoms
-
Solvated rhodium atoms, prepared by the metal vapour synthesis technique, promote the silylformylation reaction of variously substituted alkynes R1R2CH(CH2)nC≡CH, with catalytic activities comparable with and even higher than more common species such as Rh4(CO)12. Z-Silylalkenals are exclusively formed in high yields (60-95%) indicating syn addition both of CO and of the silane (Me2PhSiH) to the triple bond. The chemoselectivity of the process (silylformylation vs. hydrosilylation) is highly affected by the amount of catalyst employed (mmol of Rh species with respect to the alkyne reagent), by the steric requirements of the acetylenic substrates and by the hydrosilane/alkyne molar ratio. When optically active acetylenes are treated in the presence of Me2PhSiH under carbon monoxide pressure, the silylformylation reaction occurs with total retention of stereochemistry of the stereogenic centre, even if it is at the α-position of the unsaturated moiety, to afford enantiomerically enriched β-silylalkenals.
- Aronica, Laura Antonella,Terreni, Silvia,Caporusso, Anna Maria,Salvadori, Piero
-
p. 4321 - 4329
(2007/10/03)
-
- Nickel-catalysed electroreductive cleavage of propargyl compounds
-
The selective reduction of propargyl esters and aryl ethers, involving the cleavage of the propargyl-oxygen bond, affords the corresponding carboxylic acids and phenols in good yields. The reaction proceeds through electrosynthesis combined with the catalysis by Ni(II)-bipyridine complexes, under mild conditions.
- Olivero, Sandra,Dunach, Elisabet
-
p. 6193 - 6196
(2007/10/03)
-
- Reactions of 1,1-Dihaloalkenes with Triorganozincates: A Novel Method for the Preparation of Alkenylzinc Species Associated with Carbon-Carbon Bond Formation
-
Lithium trialkylzincates react with 1,1-dibromoalkenes 1 and 1-bromo-1-chloroalkenes 2 at -85 deg C in THF to give 1-bromoalkenes 5 and 1-chloroalkenes 7, respectively, upon hydrolysis.The intermediate (1-haloalkenyl)zincates 4 and 6 are stable at low temperature but, when allowed to warm to 0 deg C, they undergo a 1,2-alkyl migration reaction to afford alkenylzinc species 10.A variety of alkylation products 11 are obtained by the hydrolysis of 10.In the presence of (Ph3P)2Pd (5 molpercent), alkenylzinc species 10 react smoothly with organic halides (AcCl, EtOCOCl, CH2=CH(Me)Br, PhBr) to yield the corresponding coupling products 13-16.
- Harada, Toshiro,Katsuhira, Takeshi,Hara, Daiji,Kotani, Yasuo,Maejima, Keiji,et al.
-
p. 4897 - 4907
(2007/10/02)
-
- Improvement process for debrominative rearrangements
-
This invention relates to an improvement in the standard procedures involving a debrominative rearrangement reaction of a terminal dibromoolefin with activated magnesium in tetrahydrofuran.
- -
-
-
- A PRACTICAL PROCEDURE FOR THE CONVERSION OF ALDEHYDES TO TERMINAL ALKYNES BY A ONE CARBON HOMOLOGATION
-
A convenient method for the conversion of aldehydes to terminal alkynes via the corresponding 1,1-dibromoalkenes is described.The key feature of the process is the use of megnesium in tetrahydrofuran for the debromination step.
- Hijfte, Luc Van,Kolb, Michael,Witz, Pascale
-
p. 3655 - 3656
(2007/10/02)
-
- Molecular Orbital and Experimental Studies on the Photoinduced Decarboxylation of Pyrethroid Model Esters
-
A series of pyrethroid model esters with various substituents in the acid or alcohol moiety have been irradiated by u. v.-radiation (λ > 220 nm).The main reaction is decarboxylation, as evidenced by gas chromatographic (g. c.) and mass spectrometric (m. s.) analyses.In the photoinduced decarboxylation reaction, the substituent effect on the main transition, which occurs via carbonyl excitation, and on the reactivity of a radical intermediate have been examined by semiempirical molecular-orbital calculations (MNDO and CNDO/S).It has been found tha the change of benzyl carbon-oxygen bond strength in the excited states is one of the important factors in determining the yield of the decarboxylated product.
- Katagi, Toshiyuki,Mikami, Nobuyoshi,Matsuda, Tadashi,Miyamoto, Junshi
-
p. 779 - 782
(2007/10/02)
-
- REACTIONS OF 3-ALKYL- AND 3,3-DIALKYL-1-BROMOALLENES WITH ORGANOCUPRATES: EFFECTS OF THE NATURE OF THE CUPRATE REAGENT ON THE REGIO- AND STEREOSELECTIVITY
-
Organocuprates induce 1,3- and direct substitution in 3-alkyl- and 3,3-dialkyl-1-bromo-1,2-dienes leading respectively to either terminal acetylenes or allenic hydrocarbons.The nature of the cuprate exerts a prominent role in determining both the regio- and the stereochemistry of these reactions.
- Caporusso, Anna Maria,Polizzi, Carmela,Lardicci, Luciano
-
p. 6073 - 6076
(2007/10/02)
-
- Synthesis of Chiral Alk-1-ynes containing an α-Phenylethyl Group
-
(R)-4-Phenylpent-1-yne, (R)-(1b), and (S)-5-phenylhex-1-yne, (S)-(1c), have been synthesised from the corresponding chiral alk-1-enes (2) by a stereospecific bromination-dehydrobromination procedure.On the other hand, (R)-3-phenylbut-1-yne, (R)-(1a), has
- Caporusso, Anna Maria,Lardicci, Luciano
-
p. 949 - 953
(2007/10/02)
-
- Intramolecular Carbon-Hydrogen Insertions of Alkylidenecarbenes. 1. Selectivity
-
Base-promoted reaction between dialkyl ketones having γ-hydrogens and dialkyl (diazomethyl)phosphonates leads to formation of cyclopentenes in modest to high yields.The relative reactivity of various types of carbon-hydrogen bonds for the process, which involves insertion by an alkylidenecarbene, has been assessed, and the result has been compared to those reported when the carbene is generated by α elimination and by 1,2-shifts.The comparison suggests that a common species, viz., an alkylidenecarbene, may be responsible for formation of the cyclopentenes obtained from (a) flash vacuum pyrolysis of alkynes and (b) decomposition of diazoethenes, whereas that derived from α elimination of terminal vinyl halides is more selective, a result consonant with production of a carbenoid.
- Gilbert, John C.,Giamalva, David H.,Weerasooriya, Upali
-
p. 5251 - 5256
(2007/10/02)
-