Allenie alcohols

Allenie alcohols (9, 119).1 The reaction of propargylic bromides (1) with aldehydes or ketones can result in allenie alcohols (3) and/or homopropargylic alcohols (4). The selectivity depends on the substitution in 1 and 2 and is also... 

Propargyl bromide reacts with tributylstibine to form an intermediate allenylstibi-nate (A) (Table 9.62) [124], This intermediate fails to react with aldehydes at temperatures as high as 120 °C. However, addition of BuMgBr produces a reactive alleny-lantimony reagent (B), which reacts with aldehydes to yield homopropargylic alcohols. 

As discussed previously [33-36], the Lewis acid-mediated reaction of 1,2-alleny] silanes with aldehydes or ketones can also afford homopropargylic alcohols 75 or five-membered 2,3-dihydrofurans 76 [37]. The type of reaction depends on the structure of the allenylsilanes, the substituent of the silyl group and the reaction conditions. 

The 1,2-functionalization of the allene moiety in 2-azetidinone-tethered alleny-nol derivatives has also been explored [96]. Carbamate 174 was selected as the starting material for the palladium(II)-catalyzed reaction. The above carbamate was prepared from the ot-allenic alcohol 171a by treatment with tosyl isocyanate. Reaction of compound 174 was carried out at room temperature in acetonitrile in the presence of 10 mol% of Pd(OAc)2, 5 equiv of LiBr, 2 equiv of Cu(OAc)2 and 1.2 equiv of K2CO3 under an atmospheric pressure of oxygen. The 1H-XMR spectrum of the crude material displayed neither signal corresponding to the allene... 

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