Terminal alkynes and alkenes were conveniently hydroborated to the corresponding alkenyl- and alkyldichloroboranes using dichloroborane–dioxane in dichloromethane. These dichloroboranes were hydrolyzed by water to the corresponding alkenyl-and alkylboronic acids in moderate to good yields. With terminal alkenes and alkynes boron was predominantly attached to terminal carbon. Alkynes gave exclusively trans-vinylboronic ...