反应详情

Although mono-oxazolidines have been used for alkylation and alkynylation of aldehydes, the C2-symmetry of bisoxazolidine 1 provides superior results and appears to be crucial for both catalytic activity and asymmetric induction. For example, see: (a) Prasad, K. R. K.; Joshi, N. N. J. Org. Chem. 1997, 62, 3770-3771; (b) Kang, Y.; Wang, R.; Liu, L.; Da, C.; Yan, W.; Xu, Z. Tetrahedron Lett. 2005, 46, 863-865; and (c) Kang, Y. F.; Liu, L.; Wang, R.; Zhou, Y.-F. Yan, W. J. Adv. Synth. Catal. 2005, 347, 243-247. For comparison, we prepared a (1R,2S)-cis-1-amino-2-indanol-derived oxazolidine 2 using cyclohexanone instead of cyclohexanedione and tested its catalytic performance under the same reaction conditions. Alkynylation of benzaldehyde with phenylacetylene in the presence of 10 mol % of 2 gave the corresponding alcohol in only 76% yield and 17% ee (FIG. 3B).

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