Enantioselective synthesis of α-sulfenylated ketones and aldehydes via α-thiolation of metalated SAMP/RAMP hydrazones
作者:Dieter Enders、Thomas Schäfer、Wolfgang Mies
DOI:10.1016/s0040-4020(98)00481-5
日期:1998.8
Asymmetric α-sulfenylation of lithiated SAMP/RAMP hydrazones (S)-2 with disulfides afforded α-thiolated hydrazones (S,R)-3 in good yields (48–87%) and high diastereomeric excesses (91–96%). Subsequent oxidative cleavage or acidic hydrolysis of the hydrazones furnished α-thiolated ketones (R)-4a-d with high enantiomeric excesses (87–>96%). α-Sulfenylated aldehydes (R)-8a-d were prepared by a similar reaction
efficient, highly enantioselective methodology for the synthesis of α-phosphanyl ketones 7 and 2-phosphanyl alcohols 12 and 13, important hemilable ligands for enantioselective homogeneous catalysis and chiral building blocks in general, has been developed. The key step of this first enantio-selective synthesis of α-phosphanyl ketones is the diastereo-selective phosphanylation of SAMP hydrazones 2 to produce
作者:Enders, Dieter、Schubert, Heinrich、Nuebling, Christoph
DOI:——
日期:——
Asymmetric Synthesis of Heterocyclic β-Aminosulfones via Nucleophilic 1,2-Addition of 2-Lithiobenzo[b]thiophene to Aldehyde-SAMP-hydrazones
作者:Dieter Enders、Giuseppe Del Signore
DOI:10.3987/com-04-s(p)3
日期:——
An efficient asymmetric synthesis of alpha-(1,1-dioxo-2,3-dihydro-1H-1lambda(6)-benzo[b]thiophen-2-yl)-substituted amines is described. Key steps of the synthesis are the nucleophilic 1,2-addition of 2-lithio-benzo[b]thiophene to aldehyde-SAMP-hydrazones, a benzo[b]thiophene oxidation using dimethyldioxirane and a highly diastereoselective conjugate reduction with L-Selectride(R). The heterocyclic beta-aminosulfones are obtained in five steps and good overall yields (23-49%) and very high diastereo-and enantiomeric excesses (de greater than or equal to 96%, ee = 88-99%).