An efficient anti-Markovnikov selective transition metal- and solvent-free Lewis base-mediated protoboration of aromatic and aliphatic alkenes with bis(pinacolato)diboron (B2pin2) as the boron reagent is reported. This protocol is practical and demonstrates broad substrate scope and good functional-group tolerance on alkenes to give synthetically useful alkyl boronate esters in excellent yields under mild reaction conditions. The gram-scale reaction further highlighted the usefulness of this method.