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A series of γ‐butyrolactam fused donor–acceptor (D–A) cyclopropanes were synthesized, and their reactivities in Lewis acid catalyzed [3+2] annulations with aromatic aldehydes and aldimines were studied. A range of γ‐butyrolactam fused tetrahydrofurans and γ‐butyrolactam fused pyrrolidines containing four contiguous stereogenic centers were generated in good‐to‐excellent yields and with exclusive diastereoselectivities and high enantiospecificity under the catalysis of 1 mol‐% of Al(OTf)3. [ABSTRACT FROM AUTHOR]

The [3+2] annulation reaction of γ‐butyrolactone fused cyclopropanes with aldehydes or ketones under Lewis acid catalysis is described. Compared to their parent donor–acceptor (D–A) cyclopropanes, such fused bicyclic cyclopropanes demonstrated much better reactivity in this type of annulation process, providing accesses to densely substituted γ‐butyrolactone fused tetrahydrofurans bearing multiple adjacent stereogenic centers with a low catalyst loading (1–5 mol‐%), excellent diastereoselectivity, and a broad substrate scope under mild reaction conditions. [ABSTRACT FROM AUTHOR]

The stereoselective [3+2] annulations of cis-2,3-disubstituted cyclopropane 1,1-diesters with cyclic/acyclic aliphatic ketones were effected by AlCl3 to provide highly functionalized spirotetrahydrofurans in moderate to excellent yields under very mild conditions. [ABSTRACT FROM AUTHOR]

Title compounds (I) are found to be significantly more reactive than their corresponding trans-isomers in the annulation reaction with isothiocyanates (II). [ABSTRACT FROM AUTHOR]

An unprecedented ring-opening mode of trans -2-aroyl-3-aryl-cyclopropane-1,1-dicarboxylates involving the cleavage of the C2 C3 bond of the cyclopropane ring mediated by PCl 5 was disclosed. This reaction provides an efficient metal-free way to functionalized stereodefined trisubstituted Z -vinyl chlorides in moderate to good yields. A tentative mechanism for the reaction has been proposed. [ABSTRACT FROM AUTHOR]