Recyclable gallium(III) triflate-catalyzed [4+3] cycloaddition for synthesis of 2,4-disubstituted-3H-benzo[b][1,4]diazepines
摘要:
Simple and efficient Ga(OTf)(3)-catalyzed [4+3] cycloaddition of 1,3-diarylpropynones and o-phenylenediamines is developed for the preparation of 2,4-disubstituted-3H-benzo[b][1,4]diazepines. The reaction has advantages of using a green solvent, generating a minimal amount of waste, and easy catalyst recycle. (C) 2013 Elsevier Ltd. All rights reserved.
Dissecting Alkynes: Full Cleavage of Polarized C≡C Moiety via Sequential Bis-Michael Addition/Retro-Mannich Cascade
作者:Saumya Roy、Maria P. Davydova、Runa Pal、Kerry Gilmore、Genrikh A. Tolstikov、Sergei F. Vasilevsky、Igor V. Alabugin
DOI:10.1021/jo201259j
日期:2011.9.16
The reaction of diaryl ketoalkynes with 1,2-diamino ethane leads to e full scission of the triple bond with the formation of acetophenone and imidazoline fragments. In this transformation, one of the alkyne carbons undergoes formal reduction with the formation of three C-H bonds, whereas the other carbon undergoes formal oxidation via the formation of three C-N bonds (one pi and two sigma). Computational analysis confirmed that the key fragmentation step proceeds via a six-membered TS in a concerted manner. Both amines are involved in the fragmentation: the N-H moiety of one amine transfers a proton to the developing negative charge at the enolate oxygen, while the other amine provides direct stereoelectronic assistance to the C-C bond cleavage via a hyperconjugative n(N)->sigma*(C-C) interaction.
Nishio, Takehiko; Tokunaga, Tatsuhiro; Omote, Yoshimori, Journal of Heterocyclic Chemistry, 1985, vol. 22, p. 405 - 407