Favorskii-Babayan reaction

This reaction was initially reported by Favorskii in 1905 and subsequently extended by Babayan in 1939. It is a base-promoted or -catalyzed ethynylation of aldehydes and ketones to produce secondary or tertiary acetylenic alcohols or glycols using anhydrous KOH or NaOH. Therefore, it is generally known as the Favorskii-Babayan reaction or Favorskii reaction. Although it has been proposed that this reaction might involve a reaction between acetylene and the adduct from the ketone and KOH or a coupling of potassium acetylide with the carbonyl compounds, the most recent experimental results indicate that potassium hydroxide and acetylene first form a complex, rather than potassium acetylide in liquid ammonia, which then reacts with carbonyl compounds to form the acetylenic alcohols, where ammonia functions as a co-catalyst. The experimental evidence includes... 

Other references related to the Favorskii-Babayan reaction are cited in the literature. ... 

The catalyst system for the coupling reaction was a Pd(II)-tri-phenylphosphine complex, usually prepared in situ, with excess triphenyl-phospUne and either cuprous iodide or cupric acetate as a co-catalyst. Alternatively, a preformed catalyst mixture prepared from these reagents may be utilized (see Experimental Section). When 2-methyl-3-butyn-2-ol was used as the protected acetylene, the intermediates 5a-d were converted to the corresponding aryl acetylenes 6a-d by a retro-Favorskii-Babayan (8) reaction utilizing potassium r-butoxide in toluene under conditions of slow distillation. In the case of p-iododimethylaniline (3e), trimethylsilylacetylene was used as the ethynyl source. The intermediate (5e) was treated with hydroxide to generate the free aryl acetylene 6e. The syntheses of 6d and 6e are described in the Experimental section below. 

This reaction is related to the Favorskii-Babayan Synthesis and Nef Synthesis. 

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