title: A simple and mild synthesis of 1H-isochromenes and (Z)-1-alkylidene-1,3-dihydroisobenzofurans by the iodocyclization of 2-(1-alkynyl)benzylic alcohols.
abstract: A variety of iodo-substituted isochromenes, dihydroisobenzofurans, and pyranopyridines are readily prepared in good to excellent yields under mild conditions by the iodocyclization of readily available 2-(1-alkynyl)benzylic alcohols or 2-(1-alkynyl)-3-(hydroxymethyl)pyridines. Reactions are carried out in MeCN at 25 degrees C with 3 equiv of I(2) as the iodine source and NaHCO(3) (3 equiv) as the base. The regiochemical outcome of the reaction strongly depends on the substitution pattern of the starting material. In particular, the 5-exo-dig cyclization mode, leading to dihydroisobenzofurans, is observed in the case of substrates bearing a tertiary alcoholic group, owing to the gem-dialkyl effect, while the 6-endo-dig cyclization mode, leading to isochromene or pyranopyridines, is the usually preferred pathway in the case of substrates bearing a primary or secondary alcoholic group.
authors.affiliation: Dipartimento di Chimica, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Mancuso
authors.forename: Saurabh
authors.initials: S
authors.lastname: Mehta
authors.forename: Bartolo
authors.initials: B
authors.lastname: Gabriele
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Salerno
authors.forename: William S
authors.initials: WS
authors.lastname: Jenks
authors.forename: Richard C
authors.initials: RC
authors.lastname: Larock
mesh_terms: D000466:Alkadienes / Q000138:chemical synthesis* / Q000737:chemistry; D001572:Benzofurans / Q000138:chemical synthesis* / Q000737:chemistry; D001578:Benzopyrans / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D003500:Cyclization; D007455:Iodine / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D000466:Alkadienes; D001572:Benzofurans; D001578:Benzopyrans; D007455:Iodine