Carbonyl insertion reactions of ethyl .alpha.-trimethylsilyldiazoacetate. An improved route to diazoacetate aldol products

Abstract

Initial attempts in our laboratory to directly generate 1a from 1b by reductive debromination have not met with success. Most surprising was the failure of tri-n-butyltin hydride to produce any volatile products on reaction with 1b in mineral oil. (4) (a) D. C. Law and S. W. Tobey, J. Am. Chem. Soc., 90, 2376(1968; (b) related work described in ref 1.(5) (a) R.

Carboxylate Catalysis: A Catalytic O-Silylative Aldol Reaction of Aldehydes and Ethyl Diazoacetate

“…To overcome this limitation, milder catalytic methods and other variants have been published. In 1976, Evans and co-workers described a mild O -silylative variant which required the use of TMS-activated diazoacetate and catalytic KCN/18-crown-6 . Even milder methods employing, among others, DBU, quaternary ammonium hydroxide, mixed La 2 O 3 /MgO, or benzoic acid as catalysts have been disclosed.…”

“…In 1976, Evans and co-workers described a mild O -silylative variant which required the use of TMS-activated diazoacetate and catalytic KCN/18-crown-6. 5 Even milder methods employing, among others, DBU, 6 quaternary ammonium hydroxide, 7 mixed La 2 O 3 /MgO, 8 or benzoic acid 9 as catalysts have been disclosed. With metal phenolates or organometallic bases, the reaction has also been rendered enantioselective 10 ( Scheme 1 ).…”

Carboxylate catalysis: a mild catalytic O-silylative aldol reaction of aldehydes and ethyl diazoacetate

“…In 1976, Evans and co-workers described a mild Osilylative variant which required the use of TMS-activated diazoacetate and catalytic KCN/18-cr-6. 5 Even milder methods employing, among others, DBU , or benzoic acid 9 as catalysts have been disclosed. With metal phenolates or organometallic bases, the reaction has also been rendered enantioselective.…”

Carboxylate catalysis: a mild catalytic O-silylative aldol reaction of aldehydes and ethyl diazoacetate

“…In 1976, Evans and co-workers described a mild Osilylative variant which required the use of TMS-activated diazoacetate and catalytic KCN/18-cr-6. 5 Even milder methods employing, among others, DBU…”

“…: Optimization of the TMAP-catalyzed diazoaldol-type reaction *Conversion to product, determined by 1 H NMR In dry acetonitrile, the reaction is generally over in 5-10 min after adding 1-10 mol% of the catalyst (Table1, entries[4][5][6][7][8]. Only with very low catalyst loading (0.1 mol%, see entry 9), the reaction takes 24 h to reach completion.…”