ABSTRACT
Background In the rst part of this series,[1] we showed that trialkylboranes and especially commercial solutions of Et3B are ecient reducing agents that permit the conversion, at room temperature, of S-alkylxanthates, iodides and O-alkylxanthates into the corresponding alkanes with good to excellent yields. Such a process complies with the long-standing pursuit of an environmentally acceptable process for desulfurisation, dehalogenation or deoxygenation that operates under mild reaction conditions. In this context, special attention must be paid to a paper published by Jaszberenyi and Barton in 1990.[2] e authors described a reduction process of O-alkylxanthate and related compounds with Bu3SnH/Et3B/air at room temperature. ey mentioned very briey that when Bu3SnH was omitted, the reduction still occurred. e O-cyclododecyl S-methylxanthate derived from cyclododecanol aorded cyclododecane in a remarkable 62% yield. No hypothesis about the origin of the hydrogen atom that replaced the original xanthate function was proposed. Recently, as the work reported here was largely completed as already mentioned in the rst part of this series,[3,4] Wood and coworkers also observed an “anomalous” reduction of a closely related tertiary O-alkylxanthate into the corresponding alkane instead of an expected rearrangement.[5] In a subsequent report on the reduction of B-alkylcatecholboranes, Renaud and coworkers showed that the O-H bond in methanol may also be the source of hydrogen. However, the deuterium incorporations in experiments aimed at elucidating the mechanism are relatively low,[6] and obviously the experimental results do not support the hypothesis that the O-H group is the sole source of the hydrogen transferred.
