Environ-friendly approaches to densely functionalized β-lactams
摘要:
A convenient approach to densely functionalized alpha-allyl-beta-lactams has been developed using organometallic reagents and alpha-keto-beta-lactams. Indium mediated Barbier reaction in aqueous media proceeded with a higher level of diastereoselectivity and chemical yield than zinc mediated Barbier reaction in anhydrous organic solvents. (C) 1997, Elsevier Science Ltd.
Preparation of .alpha.-Methylene and .alpha.-Ethylidene .beta.-Lactams via the Ester Enolate-Imine Condensation Using .beta.-(Dialkylamino) Esters as Starting Materials: Scope and Synthetic Applications
摘要:
A new, simple procedure for the preparation of appropriately substituted alpha-methylene and alpha-ethylidene beta-lactams via the ester enolate-imine condensation is described. The method is based on the use of lithium 3-(dialkylamino) ester enolates as synthetic equivalents of the corresponding acrylate alpha-anions. Thus, the reaction of lithium enolates of 3-(dialkylamino) esters with imines produced alpha-[(dialkylamino)alkyl] beta-lactams stereoselectively and in high yield. Upon dehydroamination the latter furnished a variety of alpha-alkylidene beta-lactams. The synthesis of 3-alkylidene-4-formyl-2-azetidinones is a particularly significant feature of this work. Preparation of functionalized alpha-keto beta-lactams and beta-lactam-furan hybrids through a dihydroxylation-oxidation process starting from different alpha-alkylidene derivatives is also described. In addition, reduction of various 4-functionalized (Z)- and (E)-3-ethylidene-2-azetidinones yielded the corresponding 3-ethylideneazetidines as advanced precursors of polyoximic acids.
N,N-Dimethylphosphoramidic dichloride: a convenient reagent for the preparation of β-lactams from acetic acids and imines
作者:Fernando P Cossío、Iñaki Ganboa、Jesús M García、Begoña Lecea、C Palomo
DOI:10.1016/s0040-4039(00)96016-7
日期:1987.1
A convenient reagent for the preparation of β-lactams from aceticacids and imines is described. A new route to α-keto-β-lactams from 3-bis(ethylthio)β-lactams is also reported. Reaction of 4-acethyl-β-lactams with diazomethane is also made.
COSSIO, FERNANDO P.;GANBOA, INAKI;GARCIA, JESUS M.;LECEA, BEGONA;PALOMO, +, TETRAHEDRON LETT., 28,(1987) N 17, 1945-1948
作者:COSSIO, FERNANDO P.、GANBOA, INAKI、GARCIA, JESUS M.、LECEA, BEGONA、PALOMO, +
DOI:——
日期:——
Preparation of .alpha.-Methylene and .alpha.-Ethylidene .beta.-Lactams via the Ester Enolate-Imine Condensation Using .beta.-(Dialkylamino) Esters as Starting Materials: Scope and Synthetic Applications
A new, simple procedure for the preparation of appropriately substituted alpha-methylene and alpha-ethylidene beta-lactams via the ester enolate-imine condensation is described. The method is based on the use of lithium 3-(dialkylamino) ester enolates as synthetic equivalents of the corresponding acrylate alpha-anions. Thus, the reaction of lithium enolates of 3-(dialkylamino) esters with imines produced alpha-[(dialkylamino)alkyl] beta-lactams stereoselectively and in high yield. Upon dehydroamination the latter furnished a variety of alpha-alkylidene beta-lactams. The synthesis of 3-alkylidene-4-formyl-2-azetidinones is a particularly significant feature of this work. Preparation of functionalized alpha-keto beta-lactams and beta-lactam-furan hybrids through a dihydroxylation-oxidation process starting from different alpha-alkylidene derivatives is also described. In addition, reduction of various 4-functionalized (Z)- and (E)-3-ethylidene-2-azetidinones yielded the corresponding 3-ethylideneazetidines as advanced precursors of polyoximic acids.
Environ-friendly approaches to densely functionalized β-lactams
作者:M. Jayaraman、Maghar S. Manhas、Ajay K. Bose
DOI:10.1016/s0040-4039(96)02421-5
日期:1997.2
A convenient approach to densely functionalized alpha-allyl-beta-lactams has been developed using organometallic reagents and alpha-keto-beta-lactams. Indium mediated Barbier reaction in aqueous media proceeded with a higher level of diastereoselectivity and chemical yield than zinc mediated Barbier reaction in anhydrous organic solvents. (C) 1997, Elsevier Science Ltd.