Rh-catalyzed asymmetric hydrogenation of 2-substituted 4H-thiochromenes and 4H-chromenes was successfully developed. This method provided highly efficient access to a series of chiral 2-substituted thiochromanes and chromanes in high yields with excellent enantioselectivities (up to 99% yield, 86–99% ee). The obtained chiral 2-substituted thiochromane products were also successfully transformed to
Directing Group Assisted Copper-Catalyzed Chemoselective <i>O</i>-Aroylation of Phenols and Enols Using Alkylbenzenes
作者:Saroj Kumar Rout、Srimanta Guin、Arghya Banerjee、Nilufa Khatun、Anupal Gogoi、Bhisma K. Patel
DOI:10.1021/ol401682a
日期:2013.8.16
By using alkylbenzenes as aroyl surrogates, copper(II) catalyzed chemoselective O-aroylations of 1,3-dicarbonyl compounds and phenolic -OH ortho to carbonyl (-CHO, -COR) groups have been achieved. A dual mechanism operating in tandem for these transformations has been supported by a crossover experiment.
The synthesis of epoxides 2 by epoxidation of flavones 1 with isolated dimethyldioxirane (as acetone solution) at subambient temperatures is reported. These labile epoxides were isolated and completely characterized by UV, IR, H-1 and C-13 NMR, MS, and C, H analyses. Warming to room temperature led to rearrangement to afford quantitatively the 3-hydroxyflavones 3b,h,i,n. Treatment of the epoxides 2b,f with methanol led to the 3-hydroxy-2-methoxyflavanones 4b,f as a mixture of cis and trans isomers.
HOGALE M. B.; DHORE N. P.; SHELAR A. R.; PAWAR P. K., ORIENT J. CHEM., 2,(1986) N 1, 55-57
作者:HOGALE M. B.、 DHORE N. P.、 SHELAR A. R.、 PAWAR P. K.
DOI:——
日期:——
HOGALE, M. B.;PAWAR, B. N.;NIKAM, B. P., J. INDIAN CHEM. SOC., 64,(1987) N 8, 486-487