A facile procedure for synthesis of dihydrocoumarin derivatives was described. Although the yield of the products in the reaction of phenols with acrylates in trifluoroacetic acid in the presence of Pd(OAc)2 giving coumarins was found to be very low, dihydrocoumarin derivatives were obtained in good to high yields in the absence of Pd(OAc)2 when ethyl cinnamates bearing electron-donating groups were
Molecular iodine catalyst promoted synthesis of chromans and 4-aryl-3,4-dihydrobenzopyran-2-ones via [3+3] cyclocoupling
作者:Mayuri M. Naik、Durga P. Kamat、Santosh G. Tilve、Vijayendra P. Kamat
DOI:10.1016/j.tet.2014.05.093
日期:2014.8
Molecular iodine as an inexpensive catalyst is described in the construction of 2-substituted or 2,2-disubstituted chromans and 4-aryl-3,4-dihydrobenzopyran-2-ones via [3+3] cyclocoupling. For the synthesis of chromans, phenols and allylic alcohols were refluxed in chloroform in presence of 20 mol % I-2 while [3+3] cyclocoupling of phenols and cinnamic acids proceeded to give 4-aryl-3,4-dihydrobenzopyran-2-ones using 30 mol % I-2. Later reaction occurs via a tandem hydroarylation-esterification process at 120-130 degrees C under solvent free conditions. Chromans were obtained in 20-92% yields and substituted 4-aryl-3,4-dihydrobenzopyran-2-ones were obtained in 5-85% yields. (C) 2014 Elsevier Ltd. All rights reserved.
Das; Venkataiah; Ravindranath, Journal of Chemical Research - Part S, 2000, # 12, p. 556 - 557