Novel 1,3,2-dioxaborinanes of the general formula ##STR1## wherein R1 is a straight-chain or branched alkyl group having 1 to 20 carbon atoms, a phenyl group or bromine, Y is a 1-oxy-2-thioethyl group, a 1-oxy-4-thiophenyl group or oxygen, each group Z independently of the others is a straight-chain or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl, bicycloalkyl or cycloalkylalkyl