Metal-catalyzed alkyne hydroalkoxylation

The transition metal-catalyzed addition of alcohols to unsaturated systems has not been widely investigated. Reports on addition of alcohols to 1,3-diene [24] or allene [25] have appeared but have very limited scope. We recently reported the palladium/benzoic acid-catalyzed inter- and intramolecular addition of alcohols to alkynes in which various acyclic and cyclic allylic ethers are produced [26], The Pd-catalyzed addition of alcohols to alkylidenecyclopropanes proceeds smoothly providing a powerful tool for synthesis of allylic ethers [27a]. An intramolecular version of the hydroalkoxylation has been demonstrated in which the phenol-tethered alkylidenecyclopropanes undergo facile cyclization to give exomethylene products [27b],... 

Transition metal-catalyzed addition of heteroatom-hydrogen bonds to alkynes in syntheses of cyclic amines and pyrroles by hydroamination reactions, in syntheses of O-heterocycles by hydroalkoxylation of alkynes, and in syntheses of S- and Se-heterocycles 04CRV3079. 

Transition Metal-Catalyzed Hydroalkoxylation of Internal Alkynes... 

Scheme 38 Transition-metal catalyzed hydroalkoxylation of internal alkynes in the synthesis of spiroacetals...

Despite the successes of the gold-catalyzed addition of O-nucleophiles to alkynes, the corresponding catalyzed reactions involving nucleophilic addition to olefins are very limited. Mild, metal-catalyzed additions of O-H bonds across olefins have been studied for decades, and efforts to develop such processes have intensified in the last years. Results of the hydroalkoxylation of alkenes are collected in different reviews [1, 94-96, 161]. 

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