Coumarins are ubiquitous in plant kingdom and have been used as antitumor, antifungals, anticoagulants, insecticides. Chalcones are also widespread in plant kingdom and have been known to possess diverse biological activities; antibacterial, antifungal, antitumor and anti-inflammatory, etc. As they are considered as important natural products, numerous synthetic approaches have been reported up to the present. We devise a new selective method of preparing dihydrocoumarins and chalcones from aryl cinnamates by the selection of reagents. Dihydrocoumarin derivatives were prepared selectively by using intramolecular cyclization catalyzed by p-toluene sulfonic acid. Also, chalcones were prepared by Fries-rearrangement catalyzed by TiCl4. This method can be used for preparing various coumarin & chalcone compounds.
ProductSelectivity (3:4) Yield a (%) 1 p-TSA 1.5 neat 160 24 100:0 81 2 p-TSA 1.5 CH2Cl2 160 24 100:0 50 3 p-TSA 1.5 benzene 160 24 100:0 65 4 p-TSA 1.5 toluene 160 24 100:0 70 5 p-TSA 1.5 neat 140 4 100:0 83 6 MeSO3H 8 neat 160 24 100:0 40 7 MeSO3H 8 CH2Cl2 160 24 100:0 27 8 MeSO3H 8 benzene 160 24 100:0 55 9 MeSO3H 8 toluene 160 24 100:0 55 10 TiCl4 2 neat 160 24 0:100 68 11 TiCl4 2 CH2Cl2 160 24 0:100 60 12 TiCl4 2 benzene 160 24 0:100 71 13 TiCl4 2 neat 130 0.3 0:100 74 14 InCl3 1.5 neat 160 24 100:0 50 15 SnCl4 1.5 neat 160 24 100:0 60 a Silica gel column purified isolated yield.