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IV. Compounds with Phosphorous–Hydrogen Bonds

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    The search for less problematic hydrogen-atom transfers for use in the Barton-McCom­bie reaction has led to com­pounds with phos­phorus–hydrogen bonds. These include dialkyl­phos­phine oxides (11), alkyl phosphites (12), hypo­phos­phorous acid (13), and salts of hypo­phos­phorous acid (14) (Figure 2). All of these compounds can function as inexpensive, nontoxic hydrogen-atom transfers that form the chain-carrying radicals needed for reaction and do not produce by­pro­ducts difficult to remove.3,10,57 An example of a reaction in which hydrogen donation is from a P–H bond is shown in eq 13.58



    Alkyl phosphites (12) are excellent hydrogen-atom transfers, but reactions involv­ing these com­pounds have the disadvantage of not being able to be initi­ated by 2,2'-azobis(isobutyronitrile); ben­zoyl peroxide usually is the initi­ator.3,10 Reac­tions in which the hydrogen-atom transfer is a dialkyl­phosphine oxide (11), hypophosphorous acid (13), or a salt of hypo­phos­phorous acid (14) can be initiated by AIBN.9,57 Because it is difficult to completely remove water from hypo­phos­phorous acid and its salts, these donors are less attrac­tive choices when moisture sen­si­tive compounds are reacting.9

    This page titled IV. Compounds with Phosphorous–Hydrogen Bonds is shared under a All Rights Reserved (used with permission) license and was authored, remixed, and/or curated by Roger W. Binkley and Edith R. Binkley.

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