Anion relay chemistry

The third section of the chapter describes recently developed anion relay chemistry (ARC) involving threefold domino Sj -Brook rearrangement/ reactions, discovered by Tietze and extensively explored by Amos Smith 111 and his group. These reactions are also initiated by nucleophihc ring opening of epoxides, usually by silyl-substituted dithiane anions, and find useful apphcation in natural product synthesis. 

Scheme 4.32 Domino reactions involving (a) Type I and (b) Type II anion relay chemistry (ARC).

Scheme 4.35 Diversity oriented synthesis of 2,4,6-trisubstituted piperidines via Type II anion relay chemistry.

One of the most used sequential component reactions in the asymmetric construction of chiral compounds is the so-called anion relay chemistry (ARC) [2], This linchpin coupling protocol consists in the alkylation of an anion, generally a silyl lithium dithiane derivative, by an epoxide or an aziridine, resulting in an oxy- or aza-anion, which in the presence of hexamethylphosphoramide (HMPA) or other polar solvent gives a 1,4-Brook rearrangement, thereby leading to a new reactive dithiane anion that is capable of reacting with a second electrophile E+ (Scheme 11.1). 

Smith, A. B. Ill, Xian, M. (2006). Anion relay chemistry an effective tactic for diversity oriented synthesis. Journal of the American Chemical Society, 128, 66-67. 

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