The ratios of addition to insertion products in the reaction of benzyne with biphenyl-&,, and benzyne-d4 with biphenyl in this study were 5.1 and 3.8, respectively. 6 Although benzyne in solution reacts as a dienophile,'the ratio of addition to insertion products in the reactions of benzyne from phthalic anhydride with different reagents varies over a wide range. s See Table V.