Propar gylic alcohol

Other additions to the triple bond of disubstituted conjugated enynols, bearing a propar-gylic alcohol moiety, were reported but proceeded in extremely low yields15,106. 

Midland and Graham completed a total synthesis of (-)-pestalotin (81)33 (Scheme 4.3bb). The asymmetric reduction of the ketone 82 gave the propar-gylic alcohol 83 with high enantioselectivity. Partial reduction of the alkyne,... 

AppHcation of the intramolecular bis-silylation to disilanyl ethers of propar-gylic alcohols 53 provides a new entry into oxasilethanes 54, highly strained four-membered ring compounds including Si-O bonds (Eq. 23) [50,51]. 

Sc(OTf)3, AcOH, p-nitrobenzoic anhydride or Sc(OTf)3, AC2O, 66% to >95% yield. The lower yields are obtained with allylic alcohols, but propar-gylic alcohols give high yields. Phenols are effectively acylated with this catalyst, but at a much slower rate than simple aliphatic alcohols. The method was shown to be superior to most other methods for macrolactonization with minimum diolide formation. 

Introduction of a sUyl group, such as MesSi and (t-Bu)Me2Si, on the oxygen of a propar-gylic alcohol or on vinylaUenes affects the feasibility and the stereochemical course of intramolecular Diels-Alder reactions with an alkynyl diene, maleic anhydride or Ai-methylmaleimide. A possible explanation involves steric effects. 

In a typical example for the preparation of furans, the reaction of propar-gylic alcohol with dibenzoylmethane was carried out in the presence of a catalytic amount of [Ir(cod)(SnCl3)Cl(p-Cl)]2 combined with CS2CO3 in 1,2-dichloroethane at 80 C which gave the corresponding functionalized furanes in 67% yield (Scheme 11.21). 

The role of allylic sulfoxides as homoaldol equivalents in the synthesis of ( )-allylic alcohols was summarized earlier. A more recent finding is that allylic sulfoxides are precursors for conjugated dienes (equation 70). The elimination is regioselective but stereorandom. The 2,3-rearrangement of propar-gylic sulfenates gives allenyl sulfoxides. Allenyl sulfoxides are valuable synthetic intermediates. They can be converted into stereochemically homogeneous allenes, e.g. (205 equation 71). ... 

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