“…The MBPs 3a , 3b , 3c , 3d are stable compounds and were isolated practically unchanged after boiling in toluene for 6 h. Compounds 4a , 4b , 4c , 4d , however, could be exclusively obtained (72−80%) when the above reactions [( 1a , 1b , 1c , 1d ) + 2 ] were allowed to proceed in sodium methanolate solution containing a catalytic amount of 2,3‐dichloro‐5,6‐dicyanobenzoquinone (DDQ) .…”