Pyrroles allenyl imines

When, instead of aldehydes, A-tosyl imine 196 is used as an electrophile in a reaction with lithiated methoxyallene 183, allenyl imines 197 result. As shown in Scheme 26, they can be converted into pyrrole derivatives 198 and 199"" . 

Ila and Junjappa utilized a facile cycloisomerization of transient skipped allenyl imines 354 in the Cu(I)-catalyzed two-component 3 -b 2 synthesis of 2-thiopyrroles 355 (Scheme 8.123) [316]. The key intermediates 354 were accessed via the CuBr-promoted Sn2 substitution reaction ofpropargyl bromide 353 with N,S-acetals 352. A subsequent 5-mdo-dig cyclization afforded a variety of 1,2,3,5-tetrasubstituted and even 1,2-fused pyrroles in moderate to good yields. 

Kel in et al. reported that the copper-assisted cycloisomerization of the alkynyl imines 320 gave the pyrroles 321 in high yields (Scheme 101).169 Mechanistic studies revealed that this reaction proceeded via the propargyl-allenyl isomerization of 320 to the... 

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