Wood protection properties of quaternary ammonium arylspiroborate esters derived from naphthalene 2,3-diol, 2,2-biphenol and 3-hydroxy-2-naphthoic acid

In continuation of a program aimed at developing a boron-based, high performing and environmentally benign wood preservative suitable for outdoor use, three lipophilic tetra-n-butylammonium spiroborates, tetra-n-butylammonium bis[naphthalene-2,3-diolato(2-)-O,O borate 4, tetra-n-butylammonium bis[2,2 -biphenolato(2-)-O,O borate 5 and tetra-n-butylammonium bis[3-hydroxy-2-naphthoato(2-)-O,O borate 6 were prepared and tested. The higher molecular weight and lipophilicity of these borates compared with related borates previously examined correlates, in the case of 5 and 6, with significantly enhanced leach resistance while termiticidal activity has been maintained. The racemic spiroborate derived from 2,2 -biphenol 5, in particular, appears to be close to an optimum balance between ease of synthesis, solubility, hydrolytic stability and termiticidal activity.