Answers are grounded in this paper and cite their sources.
Exposure of the γ-ynyl-β-hydroxy-α-amino esters 14 and 16, derived from condensations between conjugated ynals and ynones 11 and the tin(II) enolate of N-tosylglycinate 12, to 0.5 equivalents of toluenesulfinic or sulfonic acid in hot toluene induces smooth 5-endo-dig cyclisation and dehydration to give good to excellent yields of the pyrroles 15 and 17.
No takes yet. Share an insight, caveat, or question.
Knight et al. (2003) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: