Arylpropargyl alcohol

The novel heliannane-type sesquiterpenoid (-)-heliannuol E was synthesized in the laboratory of K. Shishido. Interest in the total synthesis of this natural product was not only spurred by its irregular terpenoid structure and significant biological activity but the need to establish the absolute stereochemistry at the C2 and C4 stereocenters. The Sonogashira reaction was utilized to prepare the 3-arylpropargyl alcohol by coupling of a heavily substituted aryl iodide with an unprotected propargyl alcohol in quantitative yield. 

Terminal arylalkynes can be prepared by oxidation-decarbonylation of 3-arylpropargyl alcohols using manganese dioxide in the presence of alkali. The corresponding arylpiopargyl dcohols are available by palladium-catalysed cross-coupling of aryl halides with commercial propargyl alcohol. The yield of the second step can be improved by the addition of a phase-transfer catalyst (18-crown-6 Scheme 18). ... 

Tandem oxidation processes have also been applied to five-and six-membered heterocycle synthesis. New examples of six-membered rings include pyrimides and p)mdines. In one approach, an cK-arylpropargyl alcohol is oxidized to the corresponding ynone, which then reacts with ethyl a-aminocrotonate or an amidine to afford pyridines or p)Timidines, respectively (eqs 105 and 106). In both cases, the reactions were limited in scope, but the former was subsequently inproved by implementation of 8-keto esters and ammonium acetate in place of the a-amino cro-tonate s)mthon (eq 107). ... 

Isomerization of the coupling products of 1-arylpropargyl alcohols with electron-deficient halides generate a,j6-unsaturated aryl ketones, which undergo further condensation to afford heterocycles such as pyrroles and pyrimidines [25], For example, domino coupling-isomerization-condensation reactions of 1-phenylpropargyl alcohol (1", 2-bromothiazole, and methylhydrazine generated the enone 18, and the pyrazoline 19 was obtained by the reaction of methylhydrazine [25],... 

In the Sakaguchi group s total synthesis of ( )-amathaspiramide F, the key disconnection to generate the two contiguous stereocenters was based on an enolate Claisen rearrangement of aminoester 5, which could be derived enan-tioselectively from arylpropargyl alcohol 15 (Scheme 5). 

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