Next, we evaluated the light sensitivity of [6](BF4)3 by comparing its catalytic performance in this reaction under light-protected and ambient daylight conditions. The results revealed nearly identical reaction kinetics and product distribution (single product) in both cases (Fig. ). In a stark contrast, the performance of [6](BF4)3 under ambient light was strongly compromised, achieving only 63% conversion after 24 hours (Table , entry 4). To study the influence of the anions, known to have non-negligible effects on the reactivity of cationic π-acid catalysts as shown in several experimental and theoretical studies, we employed complexes [5](OTf)3 and [5](PF6)3. Indeed, with [5](OTf)3 the reaction was complete in less than an hour; yet, this rate acceleration was impaired by the formation of the 5-exo isomer 11, as a minor product. The [5](PF6)3 analogue, on the other hand, while not affecting the regioselectivity, drastically slowed down the reaction progress (Table , entries 5 and 6, and Fig. To evaluate the substrate scope of this reaction, the reactivity of complex [5](BF4)3 was tested on a representative set of three other oalkynyl biaryls, 12a-c (Scheme 5a). As with substrate 9, only the corresponding 6-endo products, 13a-c, were obtained. While the electron-rich and electronically-neutral substrates (12a and 12b, respectively) afforded the products in good yields, presence of an electron-withdrawing substituent in 12c limited the conversion to only 40% after 24h (Table , entries 1-3).