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On the conformations and relative stabilities of 1,3-disubstituted cyclobutanes

✍ Scribed by Saul Wolfe; Myung-Hwan Whangbo

Publisher: Elsevier Science
Year: 1975
Tongue: French
Weight: 242 KB
Volume: 16
Category: Article
ISSN: 0040-4039
DOI: 10.1016/s0040-4039(00)91125-0

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✦ Synopsis

Ugi and his coworkers have stated recently (1) that retention of configuration is observed in the displacement of brosylate and bromide from cis-1-OBs or Br-3-ethoxycyclobutanes under SN2 experimental conditions (LiI, NaBr, refluxing acetone, five days), and they have proposed that these reactions proceed via pentacoordinated intermediates. These are extraordinary conclusions, because of the extensive evidence that nucleophilic displacement reactions on cyclobutyl and cognate systems proceed with inversion of configuration (2). The work of Tang and Mislow (2b) is particularly relevant because, although sulfur is, in principle, a much more favorable nucleus than carbon for the detection of a pentacoordinated intermediate (31, the cisand trans-isomers of 1-ethoxy-3-methylthietanium hexachloroantimonate undergo base-catalyzed hydrolysis with essentially complete inversion of configuration (2b.4). In the experiments of Wiberg and Lampman (Za), the same equilibrium mixtures of 1,3-dichloro-, 1,3-dibromo-and 1,3-

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