New synthetic routes to β-fluoro β-phenyllactic acid derivatives and β-fluorocyanohydrins
作者:A.I. Ayi、M. Remli、R. Condom、R. Guedj
DOI:10.1016/s0022-1139(00)82265-4
日期:1981.6
Alkyl phenyl 2,3-epoxycarboxylates from the well-known Darzens glycidic esters synthesis react under very mild conditions with pyridinium-poly-hydrogen fluoride to give corresponding 3-fluoro 3-phenyllactates in almost quantitative yields with a high regio and stereoselectivity.
Asymmetric Darzenscondensation of benzaldehyde and various ketones has been investigated. The condensation of acetophenone, propiophenone and symmetric ketones with (–)-8-phenylmenthyl halogenoacetates 3a,b afforded the corresponding glycidicesters cis-12, cis-13 and 15–19 in 77–96% de, respectively, as the major products. Aza-Darzens condensation between N-benzylideneaniline and 3a occurred to give
Indium enolates were readily prepared by transmetalation of lithium enolates with indium trichloride, and were subsequently reacted with aldehydes to give β-hydroxy esters in high yields. Indium α-bromo enolates were also prepared and reacted with carbonyl compounds to give Darzens-type α,β-epoxy carbonyl products.
A general method for synthesis of cis-dicarbonyl epoxides through DBU/LiBr-cocatalyzed cyclization of α,β-dicarbonyl peroxides
作者:Zhenzhen Zong、Xiaohui Bai、Shenglin Lu、Zhiping Li
DOI:10.1016/j.tetlet.2016.07.034
日期:2016.8
A generalmethod for synthesis of cis-dicarbonyl epoxides is developed. The highly diastereoselective cyclization of α,β-dicarbonyl peroxides is achieved by DBU/LiBr cocatalysis. The coordination of lithium ion with two carbonyl groups is proposed for the control of cis selectivity.