Synfacts 2011(3): 0328-0328  
DOI: 10.1055/s-0030-1259445
Organo- and Biocatalysis
© Georg Thieme Verlag Stuttgart ˙ New York

Organocatalytic Asymmetric Ring Expansion of Cyclobutanones

Contributor(s): Benjamin List, Lars Ratjen
F. Capitta, A. Frongia*, J. Ollivier, P. P. Piras*, F. Secci
Università di Cagliari, Monserrato, Italy and Université Paris-Sud, Orsay, France
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Publication History

Publication Date:
16 February 2011 (online)


A secondary amine catalyzed ring expansion of substituted cyclobutanones with ­nitrosobenzene is reported. Surprisingly, none of the expected α-aminoxylation products was isolated and the ring-expanded products were obtained in reasonable yields, diastereo- and enan­tioselectivities. The proposed mechanism involves an enamine formation, followed by a formal nitroso aldol reaction (1). However, intermediate 2 cyclizes, presumably directed by the catalyst, and leads to bicyclic intermediate 3, which undergoes a rearrangement and hydrolysis, thus liberating the ­catalyst and product.