2-Alkenyl-thiazole derivatives

A highly efficient protocol for C2 selective alkenylation of thiazoles and benzothiazoles provides easy access to 2-alkenyl-thiazole derivatives 95 (140L1798). Interestingly, when 1-octene is used under standard conditions, the branched product 97 is obtained in 58% yield. A plausible Pd-catalyzed vinylation mechanism has been proposed. Thiazoles 93 undergoes C2 selective electrophilic C-H substitution of palladium acetate to generate the palladium(II) intermediate 98. Next, the resulting... 

Intramolecular alkenyl-alkenyl Stille cyclization was used in the synthesis of macrocydes such as Bafilomycin A [115], ( )-isocembrene [116], Lankaddins [117], Sanglifehrin [118], (-i-)-Concanamydn F [119], (-)-Pateamin [120], Apoptoli-din [121], Concanamycin F [122], (-)-Lasonolide A [123], Rhizoxin D [124], Amphi-dinolide A [125], and thiazole derivatives related to Leinamycin [126] (Scheme 6.15). 

In addition, oxazole-4-carboxylate 10 can be subjected to direct Pd-catalyzed alkenylation, benzylation, and alkylation in the 2-position [257]. Recently, direct 2-C-H-functionaUzation (alkylation and arylation) has been reported for oxazoles (as well as thiazoles and benzazoles) with free 2-position utihzing chelated Ni/Cu-catalysts derived from 2,2 -bis(dimethylamino)diphenylamine [258] or chelated Cu/Pd-complexes derived from Xantphos ]259] in the presence of a base. 

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