Reactions of p‐nitrobenzyl halides with dialkyl phosphite anions in dimethyl sulfoxide

Abstract

The reactions of p-O2NC6H4CH2Cl with (RO)2PO− in Me2SO with R = Me, Et, Pr, Bu, CF3CH2, i-Pr or Ph involve the formation of p-O2NC6H4CH2P(O)(OR)2 by SN2 substitution followed by a further SRN1 p-nitrobenzylation of p-O2NC6H4CH[P(O)(OR)2]− and p-O2NC6H4C(CH2C6H4NO2-p)[P(O)(OR)2]−. With p-O2NC6H4CH2Br, the reactions proceed mainly to form p-O2NC6H4CH, which undergoes reaction with p-O2NC6H4CH2Br to form p-O2NC6H4CH2CH2C6H4NO2-p. Halophilic reaction of (RO)2PO− with p-O2NC6H4CH(CH3)X (X = Cl, Br) leading to the bibenzyl is the preferred reaction course. Reactions of (RO)2PO− or p-O2NC6H4CH[P(O)(OR)2]− with p-O2NC6H4CH2X in Me2SO do not form significantamounts of p-O2NC6H4CHX− that would yieldp-O2NC6H4CH=CHC6H4NO2-p. However, p-Cl-C6H4CH[P(O)(OEt)2]− readily abstracts the benzylic proton from p-O2NC6H4CH2X to form the stilbene, although p-O2NC6H4CH2Br reacts with p-O2NC6H4-CH[P(O)(OR)2]− to form p-O2NC6H4CH(CH2C6-H4NO2-p)P(O)(OR)2 in a reaction mixture not inhibited by (t-Bu)2NO•. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:201–208, 1998