Nitrosobenzene as a hydrogen acceptor in rhodium catalysed dehydrogenation reactions of alcohols: synthesis of aldehydes and azoxybenzenesDedicated to Professor David Cole-Hamilton on the occasion of his retirement and for his outstanding contribution to transition metal catalysis

Acids, esters and amides have to date been the only isolated products from the dehydrogenation of primary alcohols with [Rh(trop 2 N)(L)] (trop = 5- H -dibenzo[ a , d ]cyclohepten-5yl) type complexes. With the reported method the available product family is finally to aldehydes. Using nitrosobenzene as a hydrogen acceptor the aldehydes could be isolated in up to 96% yield with substrate to catalyst ratios of up to 1000. Nitrosobenzene was found to be reductively coupled to azoxybenzene under the reaction conditions. Several symmetrically substituted azoxybenzene derivatives could be isolated in generally high yields after 2 to 4 h reaction time using a low catalyst loading. A diolefin Rh( i ) amido catalyst converts efficiently a mixture of alcohols and nitrosoarenes to aldehydes and azoxyarenes.