A novel halogenation/semipinacol rearrangement of alpha-diazo alcohol catalyzed by Lewis base has been developed through a carbene-free mechanism. This semipinacol transposition, initiated by an electrophilic halogenation (X = Cl(+), Br(+), and I(+)) of diazo carbon event, furnished a convenient synthetic route for the efficient synthesis of alpha-halo-quaternary ketones under mild conditions.
BF<sub>3</sub>·Et<sub>2</sub>O-Induced Decomposition of Ethyl 2-Diazo-3-hydroxy-3,3-diarylpropanoates in Acetonitrile: A Novel Approach to 2,3-Diaryl β-Enamino Ester Derivatives
The BF3 center dot Et2O-induced decomposition of ethyl 2-diazo-3-hydroxy-3,3-diarylpropanoates, prepared by the addition of a series of benzophenones to ethyl diazo(lithio)acetate, is reported and studied. By using acetonitrile as a solvent, the corresponding N-acyl beta-enamino ester derivatives are obtained in good yields and with a diverse regioselectivity as the result of 1,2-aryl migration in the vinyl cation intermediates. The factors that govern the migratory aptitude as well as the mechanistic aspects of the reaction are discussed.
NAGAO, KEISHIRO;CHIBA, MASATO;KIM, SANG-WON, SYNTHESIS, 1983, N 3, 197-199
作者:NAGAO, KEISHIRO、CHIBA, MASATO、KIM, SANG-WON
DOI:——
日期:——
A New Efficient Homologation Reaction of Ketones via their Lithiodiazoacetate Adducts
作者:Keishiro Nagao、Masato Chiba、Sang-Won Kim
DOI:10.1055/s-1983-30277
日期:——
Relay Rh(<scp>ii</scp>)/Pd(0) dual catalysis: synthesis of α-quaternary β-keto-esters <i>via</i> a [1,2]-sigmatropic rearrangement/allylic alkylation cascade of α-diazo tertiary alcohols
A relay Rh(ii)/Pd(0) dual catalysis that enables domino [1,2]-sigmatropic rearrangement/allylic alkylation of α-diazo tertiary alcohols is described. This transformation represents a highly efficient method for the one-pot synthesis of α-quaternary β-keto-esters under mild conditions, in which two separate C-C σ-bonds at the carbenic center were formed in a straightforward manner.