Base‐Induced Condensation of α‐Chloro Oxime Derivatives Furnishes Alkynes

Abstract

A one‐carbon unit is lost in the condensation of α‐chloro oxime ethers induced by lithium diisopropylamide [Eq. (1)]. This reaction, which provides alkynyl oxime ethers in good yields, is proposed to proceed via a 2‐(iminomethyl)azacyclobutadiene intermediate.

Synthesis of 2-Chloro-2-imidoylaziridines via Aza-Darzens-type Reaction of 3,3-Dichloro-1-azaallylic Anions and N-(Arylsulfonyl)imines

“…2 Remarkable to note is the lack of self-condensation and side-reaction products during the deprotonation of R-chlorinated and R,R-dichlorinated imines, a clear advantage in contrast to, for instance, R-chlorinated oximes. 31 Knowing that the condensation reaction of R-chlorinated imine anions with an activated imine (e.g., N-sulfonylimine) (9) (a) Casarrubios, L.; Pe ´rez, J. A.; Brookhart, M.; Templeton, J. L. J. Org.…”

“…A preceding Darzens-type reaction of α-chloroimines with ketones and aldehydes enabled the synthesis of 2-imidoylepoxide derivatives . Remarkable to note is the lack of self-condensation and side-reaction products during the deprotonation of α-chlorinated and α,α-dichlorinated imines, a clear advantage in contrast to, for instance, α-chlorinated oximes …”

Elimination Strategy for Aromatic Acetylenes

“…A review on this subject has appeared . Alkynyl oxime ethers were prepared by exposure of α-chloro oximes to LDA (Scheme ) . This reaction probably involves azacyclobutadiene intermediates.…”

Carbamoyl Anion Addition to Azirines

“…Addition of N , N -diisopropyl­formamide followed by LDA to the reaction mixture at −78 °C provided the aziridine 33 in 54% isolated yield. The reaction presumably occurs via deprotonation of the O -tosyl oxime 31 and subsequent cyclization to azirine 32 , which reacted with the concurrently generated carbamoyllithium reagent to give the aziridine 33 . This one-pot process conveniently avoids potentially dangerous azide chemistry for the formation of azirine 32 and the need to isolate and purify an unstable azirine.…”