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Regioselective One‐Pot Synthesis of Isocoumarins and Phthalides from 2‐Iodobenzoic Acids and Alkynes by Temperature Control
Author(s) -
Kumar Manian Rajesh,
Irudayanathan Francis Mariaraj,
Moon Joong Ho,
Lee Sunwoo
Publication year - 2013
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201300561
Subject(s) - isocoumarins , chemistry , regioselectivity , phthalide , sonogashira coupling , isocoumarin , organic chemistry , synthon , pretargeting , combinatorial chemistry , catalysis , palladium , radioimmunotherapy , antibody , immunology , monoclonal antibody , biology
Copper‐catalyzed coupling reaction of 2‐iodobenzoic acids and alkynes such as terminal acetylenes, alkynyl carboxylic acids, and trimethylsilylacetylene selectively afforded isocoumarins and phthalides in the presence of cesium carbonate (Cs 2 CO 3 ) and dimethyl sulfoxide (DMSO). Among the regioselective products, only the 6 ‐endo‐dig product, isocoumarin, was formed at 100 °C, and the 5‐ exo‐dig product, phthalide, was formed as a major product at 25 °C. A variety of alkynes produced the corresponding isocoumarins and phthalides in good yields. A mechanism is suggested in which the formation of 2‐alkynylbenzoic acid as an intermediate via Sonogashira‐type coupling was ruled out in the reaction pathway.