1-Pyrroline synthesis

IH of allenic amines also occurs in the presence of silver salts. IH of a-allenic amines proceeds in good yields in the presence of AgBp4 and provides a useful method for 3-pyrrolines synthesis via Endo-Trig processes (Eq. 4.93) [314]. 

Curiously, the synthesis of shihunine via a phenylcyclopropylimine (187) is the sole example of a simple pyrrolidine alkaloid obtained according to this general pyrroline synthesis (188) (Scheme 40). 

Pyrrolines, formation by 1,3-dipolar cycloaddition 84BSB593. 2-Pyrrolines, synthesis via 1,5-dipolar cyclization 79CRV181. 

Scheme 8.17 [Cu(hfacac)2] catalyzed 3-pyrrolines synthesis via intermolecular [4-1-1] cycloaddition.

Catalysts. Silver and silver compounds are widely used in research and industry as catalysts for oxidation, reduction, and polymerization reactions. Silver nitrate has been reported as a catalyst for the preparation of propylene oxide (qv) from propylene (qv) (58), and silver acetate has been reported as being a suitable catalyst for the production of ethylene oxide (qv) from ethylene (qv) (59). The solubiUty of silver perchlorate in organic solvents makes it a possible catalyst for polymerization reactions, such as the production of butyl acrylate polymers in dimethylformamide (60) or the polymerization of methacrylamide (61). Similarly, the solubiUty of silver tetrafiuoroborate in organic solvents has enhanced its use in the synthesis of 3-pyrrolines by the cyclization of aHenic amines (62). 

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