Intramolecular asymmetric olefination of binaphthyl phosphonate derivatives of 1,3-diketones
作者:Ashutosh V. Bedekar、Toshiyuki Watanabe、Kiyoshi Tanaka、Kaoru Fuji
DOI:10.1016/s0957-4166(02)00176-3
日期:2002.5
Intramolecular asymmetric Wittig-type reactions of some chiral binaphthyl phosphonates of 2,2-disubstituted 1,3-dicarbonyl derivatives were investigated. The base-mediated cyclization occurred with differentiation of two diastereotopic carbonyl groups to give non-racemic dihydronaphthalene derivatives with moderate to good enantiomeric excess. The degree of asymmetric induction depended upon the substrates and the best result was obtained with the indanedione derivatives having alkyl substituents in 58-73% yield with 82-88% e.e. The absolute structure of one of the products was unambiguously determined by X-ray analysis and some mechanistic consideration is also given. (C) 2002 Elsevier Science Ltd. All rights reserved.
Sequenced Reactions with Samarium(II) Iodide. Sequential Intramolecular Barbier Cyclization/Grob Fragmentation for the Synthesis of Medium-Sized Carbocycles
作者:Gary A. Molander、Yvan Le Huérou、Giles A. Brown
DOI:10.1021/jo001513r
日期:2001.6.1
ten-membered carbocycles via a dominoreaction composed of a cyclization/fragmentation process. 2-(Iodoalkyl)-, 2-(iodomethyl)allyl-, and 2-(2-iodomethyl)benzyl-2-methyl-3-(methanesulfonyloxy)cycloalkanones were subjected to Barbier-type reductive coupling conditions. Intermediate cycloalkanedione derivatives were also treated under similar conditions, providing bicyclic hydroxy ketones with complete
oxaziridination reaction of cyclic diketones with alkyl azides and the subsequent rearrangement of the resulting highly active intermediate, which produces a synthetically challenging chiralbicycliclactam containing a quaternarycarbon center. This procedure not only enriches the copper-nitrene-catalyzed asymmetric reactions, but also provides an alternative strategy to address the inherent challenges of catalytic