Functionalized 4-carboxy- and 4-keto-2,3-dihydropyrroles via Ni(II)-catalyzed nucleophilic amine ring-opening cyclizations of cyclopropanes.

A general synthetic approach to vinylogous 4-carboxy- and 4-keto-2,3-dihydropyrroles is reported using Ni(ClO4)2·6H2O as a Lewis acid catalyst for nucleophilic amine ring-opening cyclizations of donor-acceptor (D-A) cyclopropanes. This methodology provided good to excellent yields of functionalized 2,3-dihydropyrroles under milder reaction conditions than previously reported and is amenable to a variety of D-A cyclopropanes and primary amines.

A general intramolecular Friedel-Crafts approach to functionalized pyrrolo[3,2,1-ij]quinolin-4-ones.

An indium(III)-catalyzed intramolecular Friedel-Crafts annulation for the efficient synthesis of pyrrolo[3,2,1-ij]quinolin-4-ones is described. The products are formed in good to excellent yields (51-97%) with diastereoselectivities up to >99 : 1 dr.

Diastereoselective intramolecular Friedel-Crafts cyclizations of substituted methyl 2-(1H-indole-1-carbonyl)acrylates: efficient access to functionalized 1H-pyrrolo[1,2-a]indoles.

A general, catalytic method for the diastereoselective synthesis of functionalized 1H-pyrrolo[1,2-a]indoles via an intramolecular Friedel-Crafts alkylation of N-acyl indoles is reported. Products were obtained in excellent yields (up to 98%) with high diastereoselectivities (up to >25:1 dr).

An efficient synthesis of hydropyrido[1,2-a]indole-6(7H)-ones via an In(III)-catalyzed tandem cyclopropane ring-opening/Friedel-Crafts alkylation sequence.

An efficient Lewis acid-catalyzed cyclopropane ring-opening/Friedel-Crafts alkylation sequence of methyl 1-(1H-indole-carbonyl)-1-cyclopropanecarboxylates is reported. The protocol affords functionalized hydropyrido[1,2-a]indole-6(7H)-ones in up to 99% yield.

A catalytic homo-Nazarov cyclization protocol for the synthesis of heteroaromatic ring-fused cyclohexanones.

A general protocol for the catalytic homo-Nazarov cyclization of cyclopropyl heteroaryl ketones has been developed, which employs indium triflate as the promoter. A range of heteroaromatic ring-fused cyclohexanones was synthesized in 56-91% yield using this protocol. An example of a tandem cyclopropanation/homo-Nazarov cyclization is also reported in which the one-pot yield is greater than the overall yield of the two individual steps.

Indium-catalyzed homo-Nazarov cyclizations of alkenyl cyclopropyl ketones.

Herein, an efficient Lewis acid catalyzed protocol for the homo-Nazarov cyclizations of alkenyl cyclopropyl ketones is reported. Alkenes bearing ß-hydrogens (or silyl groups) provide 1.5:1 mixtures of methylene cyclohexenols and cyclohexenones. When no ß-hydrogens (or silyl groups) are present, only cyclohexenones are observed. Products are rapidly formed in good to high yields (up to 93%) under mild conditions and could be readily derivatized.