Phthalides biphthalyls

Phenylacetyl chloride and hydrocin-namoyl chloride are reduced at mercury to form both acyl radicals and acyl anions as intermediates [76]. From electrolyses of phenylacetyl chloride, the products include 1,4-diphenyl-2-butene-2,3-diol diphenylac-etate, phenylacetaldehyde, toluene, 1,3-diphenylacetone, and l,4-diphenyl-2,3-butanediol, and analogous species arise from the reduction of hydrocinnamoyl chloride. Reduction of phthaloyl dichloride is a more complicated system [77] the electrolysis products are phthalide, biph-thalyl, and 3-chlorophthalide, but the latter compound undergoes further reduction to give phthalide, biphthalyl, and dihydrobi-phthalide. 

Upon being electrolyzed at carbon or mercury in MeCN containing TEAP, phthal-oyl dichloride [224] is converted into 3-chlorophthalide, phthalide, and biphthalyl. However, this system is complicated by the fact that 3-chlorophthalide can itself be reduced (at a potential only slightly more negative than that needed for reduction of phthaloyl dichloride) to afford phthalide, biphthalyl, and dihydrobiphthalide. 

Electrochemical reduction of phthaloyl dichloride (73) at a carbon or mercury cathode in acetonitrile containing TEAP led to a complex array of products. Six cathodic waves observed in the CV for the reduction of phthaloyl dichloride arise from the reductions of different electrolysis products, as well as from hydrolytically formed phthalic anhydride (74),. caused by the presence of residual water in the solvent/supporting electrolyte (equation 45). From controlled potential electrolyses of phthaloyl dichloride, a variety of products including 3-chlorophthalide (75), phthalide (76), biphthalyl (77) and dihydrobiph-thalide (78) can be obtained69,70. Reduction of glutaryl dichloride (79) at a mercury cathode in acetonitrile containing 0.1M TEAP results in the formation of 5-chlorovalerolactone (80) and valerolactone (81) as minor products, and a polymeric material (equation 46)68. 

Ramirez, F., H. Yamanaka, and O. H. Basedow New Reactions of Phosphite Esters The Conversion of Phthalic Anhydride into Biphthalyl by Trialkyl Phosphites and into Phthalide-3-phosphonates by Dialkyl Phosphites. J. Amer. Chem. Soc. 83, 173 (1961). 

---