Lewis acid-promoted cycloaddition reaction of cyclopropanes with allylsilanes

Catalytic (3 + 2) annulation of donor-acceptor aminocyclopropane monoesters and indoles

The efficient catalytic activation of donor-acceptor aminocyclopropanes lacking the commonly used diester acceptor is reported here in a (3 + 2) dearomative annulation with indoles. Bench-stable tosyl-protected aminocyclopropyl esters were converted into cycloadducts in 46-95% yields and up to 95 : 5 diastereomeric ratio using catalytic amounts of triethylsilyl triflimide. Tricyclic indoline frameworks containing four stereogenic centers including all-carbon quaternary centers were obtained.

Exploitation of donor–acceptor cyclopropanes and N-sulfonyl 1-azadienes towards the synthesis of spiro-cyclopentane benzofuran derivatives

An efficient method for the synthesis of spiro-cyclopentane benzofuran derivatives via a MgI₂-catalyzed formal [3 + 2] cycloaddition reaction between donor–acceptor cyclopropanes and N-sulfonyl 1-azadienes in good yield has been developed.

Carbocycles from donor–acceptor cyclopropanes

Donor–acceptor cyclopropane annulations – not just for heterocycles.

Formal [3 + 2] and [3 + 3] Additions of Acceptor-Substituted Cyclopropylmethylsilanes to Allenylsilanes

1,3-Dipolar synthons formed from vicinal TBDPS-substituted cyclopropyl alkyl/phenyl ketones on treatment with Lewis acids such as TiCl(4) and Et(2)AlCl reacted with allenylsilanes to furnish [3 + 2] and [3 + 3] adducts with high regio- and stereocontrol. [reaction: see text]

Allylation of Donor−Acceptor Cyclopropanes

[reaction: see text] Direct allylation of glycal-derived donor-acceptor cyclopropanes has been achieved with TiCl(4) activation followed by addition of allyltrimethylsilane. The alpha diastereomer is the major product, with selectivities ranging from 3:1 to 10:1 and yields around 80%.