One pot synthesis of polycyclic oxygen aromatics. Part IV Reaction of THP ether of 2-bromomethyl phenols

Reaction of 2-bromomethyl-1-(2'-tetrahydropyranyloxy) benzene 3a with tetrachlorocatechol(TCC) in acetone in presence of anhydrous K2CO3 resulted in the formation of diastereomeric products to which cis- & trans- 6-chloro-8-hydroxy-8-(2-oxopropyl)spiro[9H-benzo[a]xanthen- 9,2'(1'H) benzofuran]-7(8H)-one (7a & 8a) structures were assigned, along with tetrachlorocatechol ethers (5a & 6a). Similar reaction of 3a with tetrabromocatechol(TBC) gave the expected monobromo compounds 7d & 8d along with the ethers 5d & 6d. When the reaction was repeated with substrates 3b-c with TCC/TBC in ketonic solvents(acetone/methyl ethyl ketone), the corresponding compounds 5b-c to 8b-c, 5e-f to 6e-f, 7e-g & 8e-h were obtained. A suitable explanation has been given for the formation of acetonyl compound 6 in this reaction