Thiazole addition approach

Dondoni and Scherrmaim published a full account of their thiazole-based approach to formyl C-glycosides. Addition of the thiazololithio species to lactone 371 gave... 

An interesting one-carbon ring closure is found in the reaction of 94 (prepared from phenylcyanothioformamide and 1,3-diphenylpropenone) with either/)-chlorobenzoyl chloride or phenyl isocyanate to give pyrrolo[3,2- thiazoles 95 and 96, respectively (Scheme 18) <1999PSS(148)117>. However, attempted extension of this reaction sequence to include acetic anhydride did not afford a pyrrolo[3,2-i71thiazole product. In a novel approach, the same workers obtained additional examples of pyrrolo[3,2- thiazoles 99 in excellent yield as the only isolable product by reaction of A-(4-chloro and 4-methylphenyl)cyanothioformamide 97 with arylidene 98 the formation of the product was rationalized via 100-103 as detailed in Scheme 19 <2005PS(180)573>. 

Although oxidative addition of C-Cl bond of thiazole, benzothiazole, and oxazole was reported as a feasible access to NHC-TM complexes by Stone in 1974, " this approach remained unexplored in the following 25 years. In 2001, Cavell and Yates demonstrated, with combined theoretical and experimental studies, that oxidative addition of the C-H bond... 

In addition, dehydration of 4-hydroxy-2-thiazolines also leads to the fully conjugated derivatives. In general, the hydroxythiazolines are intermediates in various synthetic approaches to thiazoles (see Section 3.06.9). 

To construct additional heterocycles fused to the thienothiophene system, a number of approaches other than the above-mentioned photocyclizations were used. For example, heating 2-acetylamino-3-hydroxythieno[3,2-Z>]thiophene (206) in the presence of P2S5 afforded 2-methylthieno[3,2-fe]thieno[3,2-[Pg.158]

The penem system has always been assembled by late formation of the thiazoline ring. No attempt to obtain penems by closing the azetidinone ring as the last step has ever been reported, though this strategy is well documented on penicillins [3, 4]. Approaches based either on the dehydrative condensation of thiazoline acetic acids 4 or on ketene addition to thiazoles 5, reactions known to... 

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