THE BEHAVIOR OF 4-TRIPHENYLMETHYL-1,2-BENZOQUINONE TOWARDS ALKOXY CARBONYLMETHYLENE(TRIPHENYL)-PHOSPHORANES AND TRIPHENYLPHOSPHINE IN ACETIC ANHYDRIDE

Abstract

The reaction of alkoxycarbonylmethylene(triphenyl)phosphoranes (2) with 4-triphenylmethyl-1,2-benzoquinone (1) in acetic anhydride at room temperature for 7 h led to the formation of alkyl (6-acetoxy-α,α,α-triphenyl-m-tolyl)fumarates (7), alkyl (6-acetoxy-α,α,α-triphenyl-m-tolyl)maleates (8), benzofuran derivatives (13 and 14), 3,4-diacetoxytetraphenylmethane (18) along with triphenylphosphine and triphenylphosphine oxide. The action of alcoholic HCl on the fumarates 7 give the coumarin derivatives (19) whereas the maleates 8 yielded 19 and two additional products, alkyl (6-hydroxy-α,α,α-triphenyl-m-tolyl)maleates (6) and (E)-5-triphenylmethyl-3-alkoxycarbonylmethylenebenzo[b]furan-2(3H)-ones (20). Methylation of the products 6 with methyl iodide in dry acetone and anhydrous potassium carbonate gave the corresponding methyl ethers 21. When the maleates 6 were heated in boiling toluene for about 30 h, a mixture of the coumarin derivatives 19 and (Z)-isomer of 20 was obtained. Triphenylphosphine reacted with quinone 1 in acetic anhydride to give quantitative yield of 18 with triphenylphosphine oxide. Possible reaction mechanisms are considered.

Key Words:

• Phosphoranes
• NMR spectra
• reaction mechanisms