Asymmetricconjugatealkynylation of α,β-unsaturated ketones with (triisopropylsilyl)ethynylsilanols giving β-alkynylketones took place in high yields with high enantioselectivity in the presence of chiral rhodium catalysts.
Asymmetric Organocatalytic Double-Conjugate Addition of Malononitrile to Dienones: Efficient Synthesis of Optically Active Cyclohexanones
作者:Xue-ming Li、Bo Wang、Jun-min Zhang、Ming Yan
DOI:10.1021/ol102570b
日期:2011.2.4
9-Amino-9-deoxyepiquinine efficiently catalyzed the double-conjugate addition of malononitrile to dienones. A number of 1,1,2,6-tetrasubstituted cyclohexanones were prepared in good yields, diastereoselectivities, and excellent enantioselectivities.
Hexamethonium bis(tribromide) (HMBTB) a recyclable and high bromine containing reagent
作者:Bappi Paul、Bishal Bhuyan、Debraj D. Purkayastha、Siddhartha S. Dhar、Bhisma K. Patel
DOI:10.1016/j.tetlet.2015.08.063
日期:2015.10
A recyclable and high bromine containing di-(tribromide) reagent, hexamethonium bis(tribromide) (HMBTB) has been synthesized and utilized for the bromination of various organic substrates. The spent reagent hexamethonium bromide (HMB) can be effectively recycled by regenerating and reusing it without significant loss of activity. The crystalline and stable bis(tribromide) is an effective storehouse of very high percentage of active bromine requiring just half an equivalent of it for complete bromination. Both the Br-3(-) moieties in HMBTB are nearly linear with Br-Br-Br angle of 179.55 degrees. Published by Elsevier Ltd.