109875-42-5Relevant academic research and scientific papers
Synthesis of 2,3,4,6,7,8-Hexahydro-5H-1-benzopyran-5-ones and 3-(6-Oxo-1-cyclohexenyl)alkanoic Acids by Reduction of 4,6,7,8-Tetrahydro-2H-1-benzopyran-2,5(3H)-diones
Hombrecher, Hermann,Margaretha, Paul,Tissot, Paul
, p. 1681 - 1684 (1986)
Comparative results on the reduction of 4,6,7,8-tetrahydro-7,7-dimethyl-2H-1-benzopyran-2,5(3H)-diones 1 are reported.Hydride reduction (LiAlH4 in Et2O or NaBH4 in i-PrOH) affords 2,3,4,6,7,8-hexahydro-5H-1-benzopyran-5-ones 5 in 30-60 percent isolated yi
Light-Induced Conversion of 4,6,7,8-Tetrahydro-2H-benzopyran-2,5(3H)-diones into 3,5,6,7-Tetrahydrobenzofuran-4(2H)-ones in Methanol
Hobel, Klaus,Margaretha, Paul
, p. 101 - 105 (2007/10/02)
The photochemical conversion of 4,4,7,7-tetramethyl-4,6,7,8-tetrahydro-2H-benzopyran-2,5(3H)-dione (1) into 3,3,6,6-tetramethyl-3,5,6,7-tetrahydrobenzofuran-4(2H)-one (4) in methanol does not - as previously assumed -proceed by decarbonylation of the primarily formed acyl-vinyloxy biradical 2.This conclusion results from the finding that C-2, i.e. the CH2 group, of benzofuranone 4 stems from the solvent.Similar observations were made for other benzopyrandiones 15.A reaction sequence consisting of (a) ketene elimination from 2 with formation of 2-isopropylidene-5,5-dimethyl-1,3-cyclohexanedione and (b) light-induced (reductive) H and CH2OH addition to this intermediate followed by cyclization and dehydration to 4, is proposed for the conversion 1 --> 4.
