Enantioselective Alkynylation of Aldehydes with 1-Haloalkynes Catalyzed by Tethered Bis(8-quinolinato) Chromium Complex
作者:Dmitry L. Usanov、Hisashi Yamamoto
DOI:10.1021/ja1102822
日期:2011.2.9
The first example of Cr-catalyzed asymmetric alkynylation of aldehydes with 1-iodo- and 1-bromoalkynes was developed. The use of tethered bis(8-quinolinato) chromium catalyst (3 mol %) allowed preparation of enantioenriched propargyl alcohols with good yields and enantioselectivities up to 92% ee. 1-Bromoalkynes can be activated by the introduction of a cobalt porphine co-catalyst, which enables shorter reaction times without any loss of enantiocontrol.
Brønsted Acid-Mediated Nazarov Cyclization of Vinylallenes
作者:Yen-Ku Wu、F. G. West
DOI:10.1021/jo101112t
日期:2010.8.6
Treatment of siloxy enynes with base leads to the corresponding vinylsiloxyallenes which undergo Nazarov cyclization in the presence of trifluoroacetic acid to provide the cyclized product as a mixture of regioisomers in moderate to good overall yield.