Bioinspired intramolecular Diels-Alder reaction: a rapid access to the highly-strained cyclopropane-fused polycyclic skeleton.

A bioinsipred gold-catalyzed tandem Diels-Alder/Diels-Alder reaction of an enynal and a 1,3-diene, forming the highly-strained benzotricyclo[3.2.1.0(2,7) ]octane skeleton, was reported. In contrast, a Diels-Alder/Friedel-Crafts tandem reaction occurred instead when silver salts were used as the catalyst. Although both reactions experienced the similar Diels-Alder reaction of a pyrylium intermediate with a 1,3-diene, they have different reaction mechanisms. The former proceeded with a stepwise Diels-Alder reaction, while the latter one with a concerted one.

Iron-catalyzed benzannulation reactions of 2-alkylbenzaldehydes and alkynes leading to naphthalene derivatives.

An efficient and practical method for the synthesis of naphthalene derivatives via Fe(III)-catalyzed benzannulation of 2-(2-oxoethyl)-benzaldehydes and alkynes has been developed. The system holds the advantages of cheap catalysts, wide substrate scope, and mild reaction conditions.