Next, using the optimised reaction conditions as established above (entry 5), we examined the capabilities of other commercially available alkali metal trialkylborohydrides in catalysing hydroboration of phenylacetylene. All of the other borohydrides, i.e. NaHB(s-Bu)3, LiHBEt3 and KHBEt3, led to very high anti-Markovnikov regioselectivity of 97-99% of the (E) isomer. Nevertheless, NaHBEt 3 turned out to be the most active catalyst, as conversions of 1 reached with the other borohydrides did not go over 90% for LiHBEt3 and were even smaller for NaHB(s-Bu)3 (61%) and KHBEt3 (36%). Moreover, in the case of LiHBEt3 and KHBEt3, the GC-MS analysis showed that the alkyl bisboronate ester 4 was present as a by-product in small quantity (<2%). Having established the most optimal conditions, we attempted at extending the substrate scope over substituted phenylacetylene derivatives and other aromatic and aliphatic terminal alkynes.