ChemInform Abstract: Practical Alternatives for the Synthesis of β‐Iodofurans by 5‐endo‐Dig Cyclizations of 3‐Alkyne‐1,2‐diols.

Abstract

Practical Alternatives for the Synthesis of β-Iodofurans by 5-endo-Dig Cyclizations of 3-Alkyne-1,2-diols.-3-Alkyne-1,2-diols (I), readily available from α-hydroxyketones or esters and acetylides, undergo iodocyclization by a 5-endo-dig pathway yielding highly functionalized furans after dehydration. -(EL-TAEB, GAMILA M. M.; EVANS, ANN B.; JONES, SIMON; KNIGHT, DAVID W.; Tetrahedron Lett. 42 (2001) 34, 5945-5948; Dep. Chem., Cardiff Univ., Cardiff CF1 3TB, UK; EN)

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

“…Iodine and sodium bicarbonate mixture in dichloromethane at 0 ºC was found to promote a one-pot 5 -endo-dig cyclization of 3-alkynyl-1,2-diols and subsequent dehydration to afford β-iodofurans in high yield [ 1 , 3 ]. In a follow up investigation, Knight and coworkers treated a series of 3-alkyne-1,2-diols 27 with iodine (3.3 equiv.)…”

“…Molecular iodine in acetonitrile effected regioselective iodocyclization of o -(1-alkynyl)benzenesulfonamides 54 to yield a variety of 4-iodo-2 H -benzo[ e ][ 1 , 2 ]thiazene-1,1-dioxides 55 ( Scheme 21 ) [ 45 ]. The iodocyclization step was found to tolerate a variety of functional groups such as hydroxyl, chloro, cyano, and methoxy substituent to produce a six-membered ring exclusively.…”

“…In recent years, molecular iodine has received considerable attention as an inexpensive, non-toxic, readily available reagent to effect iodocyclization and cyclodehydroiodination reactions of tethered heteroatom-containing alkenyl or alkynyl systems to afford heterocyclic compounds with many synthetic and biological applications. For example, iodine-promoted cyclization of tethered heteroatom (oxygen-, nitrogen- or sulfur-)-containing alkynes has proven to be an effective method for the synthesis of furans [ 1 , 2 , 3 ], pyrroles [ 4 , 5 ], thiophenes [ 6 , 7 ] indoles [ 8 , 9 ], benzo[ b ]furans [ 10 , 11 ], and benzo[ b ]thiophenes [ 12 , 13 , 14 ]. The pyrrole moiety is widely distributed in a large number of naturally occurring compounds which display a variety of physiological properties [ 15 ] including antibacterial [ 16 ], antiviral [ 17 ], and antioxidant activities and also inhibit cytokine-mediated diseases [ 18 , 19 ].…”