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.

A systematic investigation of ZnCl2‐catalyzed reactions of enynals with alkenes has been undertaken. Structurally unique propeller‐like products could be obtained under mild conditions. Cyclic o‐quinodimethanes (o‐QDMs) are generated through [4+2] cycloaddition between enynals and alkenes. Both electron‐poor and electron‐rich dienophiles could be used to trap the active intermediate through [4+2] cycloaddition. But [1,5]‐H shift products could also be observed when electron‐rich alkenes were used as dienophile. DFT calculations were performed to understand the reaction mechanism. A competition between the [4+2] cycloaddition and [1,5]‐H shift was proposed for the transformation of cyclic o‐QDMs. The selectivity could be affected by the properties of the substrates.magnified image

A convenient and efficient modular approach to the synthesis of polydentate NHC ligand precursors (benzimidazolium salts) containing axial chiral 1,1′-binaphthyl from 1,2-diaminobenzene and BINOL has been developed. The benzimidazolium salts could be regarded as the potential bidentate, tridentate, and tetradentate NHC ligand precursors.

Iron-Catalyzed Benzannulation Reactions of 2-Alkylbenzaldehydes and AlkynesLeading to Naphthalene Derivatives. -This new and efficient method is applicable to various substituted benzaldehydes and alkynes including diynes and triynes. FeCl3 is employed as a cheap catalyst under mild conditions. Resulting bromo derivatives such as (VIIa) and (XIIId) can be used for further functionalization reactions. -(ZHU*, S.; XIAO, Y.; GUO, Z.; JIANG, H.; Org. Lett. 15 (2013) 4, 898-901,