A direct conversion of α,β-unsaturated ketones to vinylcyclopropanes: new zirconium-mediated reaction
作者:Philippe Bertus、Vincent Gandon、Jan Szymoniak
DOI:10.1039/a908897k
日期:——
Various vinylcyclopropanes are synthesized from α,β-unsaturated ketones via a zirconium-mediated [1,2]-addition–deoxygenative cyclopropanation sequence; the latter step surprisingly proceeds under specific protic conditions.
It's a trap! Both epoxides and aziridines substituted by an aryl ketone can be reduced efficiently using visible‐light photoredox catalysts. The radicals generated were trapped by allyl sulfones, and formed α‐branched β‐hydroxy or amino derivatives with high diastereocontrol (see scheme; dtbbpy=4,4′‐di‐tert‐butyl‐2,2′‐bipyridine, ppy=2‐phenylpyridine).
The effective one-step synthesis of conjugated arylenimines from the corresponding α′-aryl-α,β-enones and amines is carried out in the presence of TiCl4. Although these adducts are air- and moisture-sensitive, they have thus been easily obtained with fair yields, while some other literature procedures were unsuccessful.
alkyl aldehydes under basic conditions led to the corresponding 2-alkylidene-1-tetralones with fair yields and complete stereoselectivities. The E-stereochemistry of the adducts has been determined through their photoisomerisation and by comparison of the 1H NMR spectra.