13434-47-4Relevant academic research and scientific papers
Benzopyrans: Part 32 - Reaction of some simple condensates of 4-oxo-4H-1-benzopyran-3-carboxaldehydes with diazomethane - Synthesis of heterocycles linked to 3-position of benzopyran
Ghosh, Chandra Kanta,Biswas, Subhabrata,Sahana, Sirin
, p. 630 - 636 (2007/10/02)
Diazomethane adds to the exocyclic alkenic bond of acrylic esters (2) and (3) (R1 = H, Me, and/or Cl); the resultant 1-pyrazoline (10) from the former gives on heating the dihydrofuran (17) whereas compound (11) obtained from the latter affords the β-methylated alkene (7).Unlike its analogues 2 and 3, the α-cyanoacrylic ester (4) on treatment with diazomethane furnishes the dihydrofuran (18), a stereoisomeric mixture of cyclopropane (20) and pyrazoline (14).The dihydrofuran (18) on heating at 180 deg C for 30 min followed by chromatography over alumina gives innearly quantitative yield cyclopropane (20).Thermal rearrangement of 18 to 20 is the first example of a reversed alkoxycarbonylcyclopropane -> 5-alkoxy-2,3-dihydrofuran transformation.When α-cyanoesters (21-24) are treated with diazomethane, no dihydrofurans are indicated.
