A general approach to polysubstituted pyrroles

Recent Advances in the Synthesis of Thiophene Derivatives by Cyclization of Functionalized Alkynes

“…Recently, several novel approaches to iodinated thiophenes have been reported, starting from readily available sulfur-containing alkynes. As an extension of the previously reported syntheses of 3-iodofuran and 3-iodopyrrole derivatives by the iodocyclization of 3-yne-1,2 diols [80,81,82,83,84] and N -protected 1-amino-3-yn-1-ols [80,85], respectively, our research group has reported a particularly facile and convenient synthesis of 3-iodothiopenes 41 by dehydrative iodocyclization of 1-mercapto-3-yn-2-ols 23 , according to Scheme 16 [86]. Reactions were carried out in MeCN at room temperature for 5 h, using molecular iodine as the electrophilic iodine species (2–3 equiv) and NaHCO 3 as the base (1–3 equiv).…”

Versatile In Situ Generated N‐Boc‐Imines: Application to Phase‐Transfer‐Catalyzed Asymmetric Mannich‐Type Reactions

“…The absolute configuration of 8 a was unambiguously determined by X‐ray crystallographic analysis after derivatization (see the Supporting Information). The obtained Mannich‐type adducts 6 a and 8 a were readily converted into multifunctional 2,3‐dihydropyrroles 9 and 10 , respectively, by treatment with iodine and pyridine after protection of the amino group with benzyloxycarbonyl (Cbz) group (Scheme ) 23. 24…”

Molecular Iodine-Mediated Cyclization of Tethered Heteroatom-Containing Alkenyl or Alkynyl Systems

“…A representative series of homopropargylic sulfonamides have been found to undergo 5- endo - dig cyclization upon exposure to excess iodine in acetonitrile in the presence of potassium carbonate to afford 4-iodo-2,3-dihydropyrroles and β-iodopyrroles substituted with ester group at the 2-position [ 4 ]. A range of 3-hydroxy-2-sulfonylamino-4-alkynes 29 was also treated with iodine–K 2 CO 3 mixture in dichloromethane to afford systems 30 , which were in turn dehydrated using methanesulfonyl chloride in dichloromethane in the presence of triethylamine to yield iodopyrroles 31 ( Scheme 11 ) [ 37 ].…”