175430-87-2Relevant academic research and scientific papers
Regio- and enantioselective synthesis of α-silyl aldehydes and ketones via SAMP/RAMP hydrazones
Enders, Dieter,Lohray, Braj B.,Burkamp, Frank,Bhushan, Vidya,Hett, Robert
, p. 189 - 200 (2007/10/03)
An efficient, highly regio- and enantioselective methodology for the synthesis of α-silyl aldehydes and ketones 2 and 6 using two different procedures was developed. Direct α-silylation of the azaenolates derived from SAMP/RAMP hydrazones 3 with various silyl trifluoromethanesulfonates resulted after oxidative removal of the chiral auxiliary in highly enantiomerically enriched α-silyl aldehydes and ketones (R)- or (S)-2. Alternatively, hydrazones 5 derived from acetaldehyde or methyl ketones were initially α-silylated followed by highly diastereoselective α-alkylation with suitable electrophiles. The latter variant allows the regiocontrolled synthesis of α-silyl ketones (S)-6 with high enantiomeric purity, not available by direct α-silylation of unsymmetrical ketone hydrazones. The absolute configuration of the resultant α-silyl carbonyl compounds 2 and 6 was derived from earlier mechanistic investigations of electrophilic substitutions via deprotonated SAMP/RAMP hydrazones and was unambiguously assigned by X-ray-crystallographical analysis of the α-silyl-SAMP hydrazone (S,R)-4c. VCH Verlagsgesellschaft mbH, 1996.
