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
Asymmetric Synthesis of β-Substituted γ-Lactams Employing the SAMP-/RAMP-Hydrazone Methodology. Application to the Synthesis of (R)-(-)-Baclofen
作者:Dieter Enders、Oliver Niemeier
DOI:10.3987/com-05-s(k)41
日期:——
A short and efficient asymmetric synthesis of beta-substituted gamma-lactams is described. Key steps are the alpha-alkylation of aldehyde SAMP-hydrazones with alkyl bromoacetates, their MMPP mediated conversion to the corresponding nitriles and a reductive cyclization with Raney Ni or Ni boride to the title pyrrolidin-2-ones. The P-substituted gamma-lactams are obtained in three steps, good overall yields (27-78%) and excellent enantiomeric excesses (ee = 93-99%). The applicability of this procedure for the asymmetric synthesis of GABAs (gamma-aminobutyric acids) is demonstrated for (R)-(-)-baclofen hydrochloride, which is obtained in 4 steps, 55% yield and 94% ee.
Enders, Dieter; Janeck, Carsten F.; Raabe, Gerhard, European Journal of Organic Chemistry, 2000, # 19, p. 3337 - 3345
作者:Enders, Dieter、Janeck, Carsten F.、Raabe, Gerhard
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%).