Pyrroles amino Heck reactions

Methyl-l,2,3,9-tetrahydro-4H-carbazol-4-one, the key building block of the neuroactive compound alosetron, was easily obtained from 3-[(2-halophenyl)(methyl)amino]cyclohex-2-en-l-one by pyrrole ring formation via Heck reaction under microwave irradiation [94], While the iodo substrate gave an excellent yield in only 30 min at 100 °C the corresponding bromo derivative converted only poorly under the same reaction conditions (Scheme 88). 

Treatment of hydrazonium salt 4 with palladium(0) led to the formation of p3UTole 5 via 5-exo-trig amino-Heck cyclization <05H(65)273>. The reaction presumably proceeds by the oxidative addition of palladium(O) into an A-Abond. An oxidative addition into the A-O bond of benzoyloximes was the key step in the 5-endo-trig amino-Heck cyclization leading to 5-fluoro-3A-pyrroles <05CC4684>. 

Tietze described a novel twofold Heck reaction of vinylpyrroles 71 with diiodobenzenes 72 as a convenient approach to the synthesis of linear pyrrole oligomers connected by divinylbenzene units 73 <01CEJ368,01SL337>. In work by others, sulfonyl substituted pyrrole-containing chromophores with amino function were prepared for use as <01TL1309>. 

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