Reactions with Reagents Bearing an spC Electrophilic Center

Reactions with Reagents Bearing an spC Electrophilic Center 

In most of the following reactions the reagent possesses two electrophilic centers, one of them being a sp hybridized carbon however. 

The only reported example of nucleophilic addition to a C C bond is intramolecular it is observed when propiolic acid is added to 2-aminothiazole producing (109) (see p. 53). 

2-Aniinohexahydrobenzothiazole -when heated -with alkyl (299-301) or aryl (302) isothiocyanates yields the 1.3-substituted thioureas (138) 

Liquid carbon suboxide added to a solution of 2-ethylaminothiarole in anhydrous ether at 0°C gives immediate formation of a white precipitate of the mesoionic xanthine (121) (R=H) (130), otherwise prepared by reaction between 2-ethylaminothiazole and phenoxycarbonyl isocyanate (see p. 65 and Ref. 304), 

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