The generality of alkynes was next investigated. As illustrated
in Table 3, various aromatic alkynes 4 cyclized with 2-
methylbenzoic acid (1a) to afford the corresponding 3-
ylidenephthalides 5 in moderate to good yields (5a−g). Both
electron-rich and -deficient phenylacetylenes were compatible
with the reaction conditions. Some reactive functional groups,
including acetyl, ester, and halogen, were tolerated under our conditions. In addition to aryl alkynes, aliphatic alkynes could
also be compatible in this transformation, delivering 5h in a
66% yield. In contrast, only either 3-alkylidenephthalides or 3-
arylidenephthalides could be accessed through the previously
reported transition-metal-catalyzed C−H coupling of benzoic
acids with unsaturated components.