- Rh-Catalyzed Synthesis of Coumarin Derivatives from Phenolic Acetates and Acrylates via C-H Bond Activation
-
An efficient annulation strategy involving the reaction of phenolic acetates with acrylates in the presence of [Rh2(OAc)4] as catalyst and formic acid as reducing agent, leading to the high yield synthesis of coumarin derivatives, has been developed. The addition of NaOAc as a base increased the yield of the products. The reaction is quite successful for both electron-rich as well as electron-deficient phenolic acetates, affording coumarins with excellent regioselectivity, and proceeds via C-H bond activation proven by deuterium incorporation studies.
- Gadakh, Sunita K.,Dey, Soumen,Sudalai, Arumugam
-
p. 11544 - 11550
(2015/12/04)
-
- Synthesis, pharmacological studies and molecular modeling of some tetracyclic 1,3-diazepinium chlorides
-
Seven new 1,3-diazepinium chlorides exhibiting some structural similarities to the 1,4-benzodiazepines were synthesized. In a Hippocratic screen using mice, three of these salts, 3-methoxy-6-oxo-7,13-dihydro-6H-benzofuro[2,3-e]pyrido[1,2-a][1,3]diazepin-12-ium chloride (8a), 3-methoxy-9-methyl-6-oxo-7,13-dihydro-6H-benzofuro[2,3-e]pyrido[1,2-a][1,3]diazepin-12-ium chloride (8c) and 3-methoxy-11-methyl-6-oxo-7,13-dihydro-6H-benzofuro[2,3-e]pyrido[1,2-a][1,3]diazepin-12-ium chloride (8e) were examined for their effect on the central nervous system, and their activities compared to that of diazepam. On their own, salts 8a, 8c and 8e solicited no sedative effects on the behaviour of the animals. However, they elicited significant effects in combination with diazepam on diazepam-induced activities such as decreased motor activity, ataxia and loss of righting reflex. Compounds 8a and 8c were fitted into the pharmacophore/receptor model developed by Cook et al. with interaction at the L1, H1 and A2 sites indicating that they are potential inverse agonists of the Bz receptor. The compounds displayed some affinity for the α1 isoform of the GABAA/BzR (LDi interaction) but are non-selective for α5 (no L2 interaction). Results of binding affinity studies showed that compound 8a is mildly selective for the α1 receptor although not very potent (Ki = 746.5 nM). The significant potentiation of diazepam-induced ataxia and decreased motor activity by compounds 8a and 8c in the Hippocratic screen may be associated with α1 selectivity.
- Grant, Julie-Ann A.,Bonnick, Tamicka,Gossell-Williams, Maxine,Clayton, Terry,Cook, James M.,Jackson, Yvette A.
-
experimental part
p. 909 - 921
(2010/05/17)
-
- Free radical chemistry associated with H(RSiH) nH
-
Polysilanes of the type H(RSiH)nH, where R = n-hexyl or phenyl, have been used as radical-based reducing agents for organic halides. They rival the effectiveness of the other group 14 hydrides in reduction processes. The repetitive hydrogen transfer from the same molecule of H(RSiH)nH allows these compounds to be used in small quantities. Lower (5 × 104 M-1 s-1) and higher (6 × 105 M-1 s-1) limit values for the rate constant of the reaction of primary alkyl radicals with each SiH moiety of H(PhSiH)nH have been obtained by using unimolecular radical reactions as timing devices. The photochemical behavior of these polysilanes in the presence or absence of di-tert-butyl peroxide have been studied by EPR spectroscopy, and the -SiHR-SiR-SiHR radical (R = n-hexyl) has been identified as a transient species. Silyl radicals, obtained from H(RSiH)nH and thermally generated tert-butoxyl radicals, add to a variety of substrates containing double bonds to give the corresponding adducts for which EPR spectra have been recorded.
- Chatgilialoglu,Ferreri,Vecchi,Lucarini,Pedulli
-
p. 475 - 481
(2007/10/03)
-
- 13C Nuclear Magnetic Resonance Spectroscopy of 4-Methylcoumarins (4- Methyl-2H-1-benzopyran-2-ones)
-
The 13C NMR spectra of 36 differently substituted 4-methylcoumarins (4-methyl-2H-1-benzopyran-2-ones) have been recorded.The effects of an alkyl side-chain at C-3 on the chemical shift values and that of a methoxy or an acetoxy group in place of a hydroxy group have been observed and rationalized.This study may be helpful in the structure elucidation of nei and natural 4-methylcoumarins. KEY WORDS 13C NMR chemical shifts 4-Methylcoumarins 4-Methyl-2H-1-benzopyran-2-ones.
- Parmar, V. S.,Singh, S.,Boll, P. M.
-
p. 430 - 433
(2007/10/02)
-
- Regioselective Mono-O-alkylation of some Pyrocatechoxide Dianions
-
In dimethyl sulphoxide the dianions derived from 2,3- or 3,4-dihydroxybenzaldehydes and 4-methylesculetin afford products corresponding to alkylation at the less acidic site while the monoanions give the isomeric phenols.
- Kessar, Satinder V.,Gupta, Yash P.,Mohammad, Taj,Goyal, Manju,Sawal, Kewal K.
-
p. 400 - 401
(2007/10/02)
-
