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In this article, a Lewis acid mediated 1,4-addition/formal [3+2] cycloaddition reaction engaging functionalized β-carboline and 1,4-benzoquinone has been demonstrated. Application of this developed technology facilitated the construction of the challenging C-9′–C-15 quaternary center linkage in the dimeric indole alkaloid, haplophytine, and enabled the preparation of an advanced key intermediate en route to the total synthesis of this historical natural product.

The synthesis of (-)-hamigeran B has been achieved, based on a new approach to cyclopentane construction, the rhodium-mediated intramolecular C-H insertion of alpha-aryl-alpha-diazoketones. The endo-isopropyl group was installed by selective hydrogenation of a cyclopropylidene substituent.

Long chain α-aryl α-diazo ketones cyclize efficiently to the corresponding cyclohexanones under Rh catalysis.

Some long chain α-aryl α-diazo ketones under Rh catalysis cyclize efficiently to the corresponding cyclohexanones. This is in marked contrast to the cyclizations of α-diazo β-ketoesters, which consistently deliver cyclopentanone products.

A trisubstituted cyclopentane chiron has been prepared by dynamic kinetic reduction of a pulegone-derived β-keto ester. This chiron served as the starting material for the synthesis of the reported structure of the tricyclic sesquiterpene trans-africanan-1α-ol. The synthetic material was not congruent with the natural product.

A synthetic route to the carboline disaccharide domain (2) of shishijimicin A (1) has been developed. The convergent synthesis relies on a novel application of the Reetz–Muller-Starke reaction to form the central, sulfur-bearing quaternary carbon center and addition of the carboline structural motif as a dianion to a disaccharide aldehyde fragment.

The synthesis of (−)-hamigeran B has been achieved, based on a new approach to cyclopentane construction, the rhodium-mediated intramolecular C−H insertion of α-aryl−α-diazoketones. The endo-isopropyl group was installed by selective hydrogenation of a cyclopropylidene substituent.

Direct diazo transfer proceeds smoothly with alpha-aryl ketones. The derived alpha-aryl-alpha-diazo ketones cyclize efficiently with Rh catalysis to give the corresponding alpha-aryl cyclopentanones.