Highly efficient non-palladium-catalyzed controlled synthesis and X-ray analysis of functionalized 1,2-diaryl-, 1,2,3-triaryl-, and 1,2,3,4-tetraarylbenzenes.

A general, two-step, highly efficient synthesis of 1,2-diaryl-, 1,2,3-triaryl-, and 1,2,3,4-tetraarylbenzenes from simple stitching of alpha-oxo-ketene-S,S-acetals and active methylene compounds via a lactone intermediate is described. This procedure offers easy access to highly functionalized arylated benzenes that contain sterically demanding groups in good to excellent yields. The novelty of the procedure lies in the construction of aromatic compounds with the desired conformational flexibility along the molecular axis in a transition-metal-free environment through easily accessible precursors. Crystal analysis of these arylated benzene scaffolds showed that the peripheral aryl rings are arranged in a propeller-like fashion with respect to the central benzene ring. Examination of the crystal packing in the structure of a 1,2,3,4-tetraarylbenzene revealed an N...pi interaction between molecules related by a two-fold screw axis running in the direction of the a axis. Interestingly, the repeating array of N...pi interactions around the axis of this 1,2,3,4-tetraarylbenzene forces the molecules into a helical pattern.