Copper-catalyzed three-component coupling/intramolecular

Recent approaches to the copper-catalyzed three-component coupling of organometaUic reagents with imines and acid chlorides employ organoindium compounds [147] or orga-nostannanes [148]. In the first case, a-substimted amides or A -protected amines are obtained, whereas the second process provides hexahydro-l/f-isoindolones via a tandem Cn-cata-lyzed three-component coupling/intramolecular Diels-Alder reaction. 

A possible mechanism for this copper-catalyzed three-component reaction was proposed in Scheme 7.21. First, coupling of 37 with hydrazine hydrochloride provides A in the presence of base (K3PO4). Copper-catalyzed coupling of A with alkyl 2-cyanoacetate (C-aiylalion) gives B, intramolecular nucleophilic attack of the NH of the pyrazolo group to cyano in B leads to C, and isomerization of C affords the target product 38. 

Recently, Ma et al. developed a three-component reaction for the synthesis of 2-A -substituted benzothiazoles 107 via the copper-catalyzed coupling of 2-iodoanilines, carbon disulfide, and secondary amines (Scheme 3.56) [149]. In these reactions, the condensation of CS with an amine in the presence of a base generates dithiocarbamate salts XXXV, which undergo coupling with 2-iodoanilines to give XXXVI and subsequent intramolecular condensation and elimination to afford the substituted benzothiazoles 107. 

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