Borane diphenylamine complex

Similar claims are also made for diphenylamine-borane, which is a solid and relatively stable re-agent. Aliphatic amine-borane complexes, however, require elevated temperatures in order to effect hydroboration.Although this is in general a serious drawback, on occasions it may be advantageous by allowing slow liberation of borane, which leads to cyclization products rather than polymers. An example of the use of triethylamine-borane in this way is shown in equation (11). ° Alternatively, methyl iodide or a Lewis acid may be added to complex the amine and thus liberate the reactive, free borane... 

The easily prepared, stable solid reagent diphenylamine-borane (Ph2NH BH8) has been shown to be more reactive than aliphatic amine-boranes and almost as reactive as borane-THF for the reduction of ketones acids are also reduced to alcohols. Polyethylene glycols (PEG) catalyse the reduction of ketones by sodium borohydride under phase-transfer (PT) conditions, for example in solid-liquid PT with PEG as solvent. The solid zinc borohydride-dimethylformamide complex reduces aldehydes and ketones to alcohols, but only one hydrogen atom from each tetrahydridoborate unit is utilized. The different rates of reduction of various classes of ketone (saturated aliphatic faster than aromatic, and a -unsaturated very slow) suggest a possible selectivity between ketones. The corresponding cadmium complex, prepared in situ, reacts similarly. Lithium methylborohydride, LiMeBHj, prepared as shown in equation (1), where... 

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