the reagent prepared from n-Bu3SnLi and Et2AlCl or from SnCl2 and Et2AlCl affords enolates which react with ketone or aldehyde to give β-hydroxy carbonyl compounds in good to excellent yields. The reactions proceed similarly with the reagents which are generated from R3PbLi (R=Ph, n-Bu) and Et2AlCl. Catalysis by the added Pd(PPh3)4 complex promotes the reduction effectively and improves the yields of
concentration of ammonia in the reaction medium. Zinc (A) prepared in liquid ammonia (Method A) was much less active then zinc (B) prepared in THF containing 10–20 volume % of liquid ammonia (Method B). The X-ray powder diffractometry data suggested that zinc (B) was less crystalline then zinc (A). The Reformatsky and Barbier type reactions of carbonyl compounds with α-bromoesters, allylic and propargylic
new approach has been demonstrated for the regiospecific aldol synthesis by the simultaneous addition of α-halo carbonyl derivatives and aldehydes or ketones to a suspension of diethylaluminum chloride and zinc in tetrahydrofuran at low temperature. This technique is also employable under mild conditions for the Reformatsky reaction to give β-hiydroxy esters in excellent yield. One of the unique synthetic
Indium mediated allylation and propargylation reactions of dimethyl acetals and ketals
作者:Jin Sun Kwon、Ae Nim Pae、Kyung Il Choi、Hun Yeong Koh、Youseung Kim、Yong Seo Cho
DOI:10.1016/s0040-4039(01)00042-9
日期:2001.3
Indium mediated allylation and propargylation reactions of acetals and ketals with various allyl or propargyl bromides in aqueousmedia successfully provided the corresponding homoallylic or homopropargylic (and allenylic) alcohol, respectively, in moderate to good yields. Highly chemoselectiveallylation is also described. The ketal and aryl acetal could be selectively allylated over the aliphatic
Treatment of α-halo carbonyl compounds with title Sn-Al or Pb-Al reagents provides enolates which react with aldehydes or ketones to give β-hydroxy carbonyl compounds effectively.