Highly Stereoselective Asymmetric Construction of an Acyclic Carbon Skeleton Having Two Adjacent Alkyl Substituents by Michael Addition of Optically Active Allenyltitaniums to Alkylidenemalonates
摘要:
[GRAPHICS]Enantio-enriched allenyltitaniums prepared in situ by the reaction of optically active secondary propargyl phosphates with a divalent titanium reagent Ti(O-i-Pr)(4)/2i-PrMgCl react readily with alkylidenemalonates with excellent regio- and diastereoselectivities to afford the Michael addition products with a high optical purity, thus opening up a new asymmetric method for construction of an acyclic carbon skeleton bearing two adjacent alkyl substituents.
Electrophilic amination of racemic and non-racemic allenyltitaniums. One-pot synthesis of α-hydrazinoalkynes from propargylic alcohol derivatives
作者:Duk Keun An、Koichiro Hirakawa、Sentaro Okamoto、Fumie Sato
DOI:10.1016/s0040-4039(99)00584-5
日期:1999.5
a reagent and dialkyl azodicarboxylates gave α-hydrazinoalkynes in good yields. The reaction, which proceeded with up to 86% chiral transfer, thus has opened up a newroute to opticallyactive α-hydrazinoalkynes from the opticallyactive propargylic compounds.
Synthesis of chiral alkynes having 2H or halogen at the secondary or tertiary propargylic stereogenic center by hydrolysis and halogenolysis of optically active allenyltitaniums having axial chirality
作者:Duk Keun An、Sentaro Okamoto、Fumie Sato
DOI:10.1016/s0040-4039(98)00830-2
日期:1998.6
The hydrolysis and halogenolysis of opticallyactive allenyltitaniums, generated by the reaction of a reagent with opticallyactive propargyl alcohol derivatives, proceed in a regioselective way and with excellent degree of chiral transfer, thus opening up a highly efficient and practical route to chiral alkynes having 2H or Cl at the stereogenic propargylic center.
Synthesis of optically active allenyltitaniums having axial chirality by the reaction of optically active propargylic compounds with a reagent
作者:Sentaro Okamoto、Duk Keun An、Fumie Sato
DOI:10.1016/s0040-4039(98)00829-6
日期:1998.6
(η2-propene)Ti(O-i-Pr)2, generated in situ from Ti(O-i-Pr)4 and 2 equiv of i-PrMgCl, with opticallyactive secondary propargyl phosphate and tertiary propargyl carbonate proceeds with more than 97% chiral transfer, thus providing an efficient and practical method for synthesizing di- and tri-substituted allenyltitaniums with high optical purity.
General synthetic method for preparation of optically active propargyl and allylstannanes
作者:Sentaro Okamoto、Shin-ichiro Matsuda、Duk Keun An、Fumie Sato
DOI:10.1016/s0040-4039(01)01247-3
日期:2001.9
reaction of chiral allenyltitaniums, generated from opticallyactive secondary propargyl phosphates and a Ti(O-i-Pr)4/2 i-PrMgCl reagent, with trialkylstannyl chloride proceeded with a high chirality transfer of more than 93% to afford opticallyactive secondary propargylstannanes in excellent yield, and which, in turn, were converted to opticallyactive (Z)-allylstannanes by reaction with Ti(O-i-Pr)4/2