Building BLOCK strategies for the synthesis of molecular clefts with inside functionality

A new general route to U-type cavity structures (molecular clefts) with ins ide functionality has been developed using wall extension or base/ roof ass embly methods which draw upon (i) the 1,3 dipolar cycloaddition reaction be tween alkenes and cyclobutene epoxides (ACE coupling) or (ii) the Diels-Ald er reaction of alkenes with fused dihydropyridazines (s-tetrazine coupling) . In this way, functional units (e.g., crown ethers, redox active naphthale nes) have been attached stereospecifically to short-walled bis-alkenes 1-5 to produce cavity structure 6-10 with top of-wall separations (C to C) from 4.5 to 12.7 Angstrom.