A Simple and Mild Synthesis of 1H-Isochromenes and (Z)-1-Alkylidene-1,3-dihydroisobenzofurans by the Iodocyclization of 2-(1-Alkynyl)benzylic Alcohols
- 31 December 2009
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Organic Chemistry
- Vol. 75 (3), 897-901
- https://doi.org/10.1021/jo902333y
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 °C with 3 equiv of I2 as the iodine source and NaHCO3 (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.Keywords
This publication has 94 references indexed in Scilit:
- Electrophilic Cyclization of 2-Chalcogenealkynylanisoles: Versatile Access to 2-Chalcogen-benzo[b]furansThe Journal of Organic Chemistry, 2009
- Competition Studies in Alkyne Electrophilic Cyclization ReactionsThe Journal of Organic Chemistry, 2008
- Expedient Syntheses of β‐Iodofurans by 5‐endo‐dig CyclisationsEuropean Journal of Organic Chemistry, 2007
- Synthesis of 2,3-Disubstituted Benzo[b]furans by the Palladium-Catalyzed Coupling ofo-Iodoanisoles and Terminal Alkynes, Followed by Electrophilic CyclizationThe Journal of Organic Chemistry, 2005
- Electrophilic Cyclization of 2-(1-Alkynyl)-2-alken-1-ones Using the I2/K3PO4 System: An Efficient Synthesis of Highly Substituted IodofuransOrganic Letters, 2005
- Solid-Phase Synthesis of 1,2,3-Trisubstituted Indoles and 2,3-Disubstituted Benzofurans via IodocyclizationJournal of Combinatorial Chemistry, 2005
- Synthesis of Highly Substituted Furans by the Electrophile-Induced Coupling of 2-(1-Alkynyl)-2-alken-1-ones and NucleophilesThe Journal of Organic Chemistry, 2005
- 5-Endo-Dig Electrophilic Cyclization of 1,4-Disubstituted But-3-yn-1-ones: Regiocontrolled Synthesis of 2,5-Disubstituted 3-Bromo- and 3-IodofuransOrganic Letters, 2005
- AuCl3-Catalyzed Synthesis of Highly Substituted Furans from 2-(1-Alkynyl)-2-alken-1-onesJournal of the American Chemical Society, 2004
- A New Approach to 2,3-Disubstituted Benzo[b]furans from o-Alkynylphenols via 5-endo-dig-Iodocyclisation/Palladium-Catalysed ReactionsSynlett, 1999