Aluminum Catalyzed Selective Reduction of Heteroallenes via Hy-droboration: Amide/Thioamide/Selenoamide Bonds Construction and C=X (X= O, S, Se) Bond Activation

An unprecedented conjugated bis-guanidinate (CBG) stabilized aluminum dihydride, [LAlH2; (L = {(ArNH)(ArN)–C=N–C=(NAr)(NHAr)}; Ar = 2,6- Et2-C6H3)] (I) catalyzed chemoselective hydroboration of heteroallenes such as carbodiimide (CDI)s, isocyanates, isothiocyanates, and isoselenocyanates is reported. A wide range of heteroallenes, including electron-donating and withdrawing groups, experience hydroboration to obtain selectively N-boryl amide, N-borylaminal, and N-boryl methyl amine products. More importantly, a single sustainable molecular aluminum-based catalyst effectively catalyzes CDIs, isocyanates, isothiocyanates, and isoselenocyanates into formamidines, formamides, thioformamides, and selenoformamides, respectively. Fur-ther, heteroallene substrates undergo hydrodeoxygenation (HDO), hydrodesulfurization (HDS), and hydrodeselenization (HDSe) reactions leading to N-boryl methyl amines. In addition, a series of control and kinetic experiments indicate that the aluminum hydride species are essential for all partial and complete reduction steps and breaking the C=X (X = O, S, and Se) bonds in het-eroallenes.