Transition-Metal-Free Interrupted-Hydrogen-Borrowing Methylenation of Ketones Using Methanol

An efficient and benign base-promoted interrupted-hydrogen-borrowing methylenation of ketones has been developed using methanol under transition-metal- and additive-free conditions. This protocol facilitates access to various 1,5-diketones and functionalized cyclopentane derivative in good to excellent yields. Conversion of 1,5-diketones to functionalized pyridine and dibenzo­[c,h]­acridine derivatives and one-pot access of former has also been achieved. Plausible mechanisms have been proposed based on preliminary mechanistic investigations and isolation of a possible trapped intermediate.