Heteroatom Chemistry Volume 12, Number 6, 2001 The Reaction of Organophosphorus Reagents with Substituted-1,3-Diphenylpropanetrione: New Synthesis of Azaphospholene Derivatives L. S. Boulos and M. H. N. Arsanious Department of Pesticide Chemistry, National Research Centre, Dokki, Cairo, Egypt Received 2 January 2001; revised 23 March 2001 ABSTRACT: The reaction of 1,3-diphenyl-2-(phe- nylimino)-3-(ylidenemethyl-acetate)-1-propanone (5) with trisdialkylaminophosphines (6a,b) in refluxing toluene afforded the new oxazaphospholene products (7a–b). On the other hand, the cyclic azaphospholene adducts 8a–b were isolated from the reaction of 5 with 6a,b without solvent. Trialkyl phosphites 1b–c react with compound 5 to give the respective dialkyl phosphate products (9a,b). Moreover, trisdialkyl- aminophosphines (6a,b) react with 2a and 2b to give the dipolar adducts 10a,b and the phosphonate products 11a,b, respectively. Possible reaction mecha- nisms are considered, and the structural assignments are based on compatible analytical and spectroscopic results. C  2001 John Wiley & Sons, Inc. Heteroatom Chem 12:511–517, 2001 INTRODUCTION We have reported [1] that trialkyl phosphites (1a–c) react with 2-(phenylimino)-1,3-diphenylpropan- edione (2a) and 2-(phenylmethylene)-1,3-dipheny- lpropane dione (2b) to give the corresponding phosphonate adducts (3a–c) and (4a–c), res- pectively (Scheme 1). As part of our continuing interest in organophosphorus syntheses [2–10], we describe here the reactivity of 1,3-(phenylimino)- 3-(ylidenemethylacetate)-1-propanone (5) toward Correspondence to: L. S. Boulos c  2001 John Wiley & Sons, Inc. trisdialkylaminophosphines (6a,b) and trialkyl phosphites (1a–c). The purpose of this study was to determine the preferential site of attack by these reagents. A comparative study on the behavior of 2a and 2b toward trisdialkylaminophosphines (6a,b) is also reported (Scheme 2). RESULTS AND DISCUSSION We have found that 1,3-diphenyl-2-(phenylimino)- 3-(ylidenemethylacetate)-1-propanone (5) [1] reacts with trisdimethylaminophosphine 6a in refluxing toluene to give a chromatographically pure adduct formulated as 7a (Scheme 3). Structure elucidation of product 7a is based on the following evidence: elemental analyses and molecular weight determi- nation (MS) of 7a support the molecular formula C 26 H 25 N 2 O 4 P (460.46 ); accordingly, MS : m/z = 460 (M + , 100% base peak). Its IR spectrum, in KBr, ex- hibits an intense band at 1240 cm −1 correspond- ing to the P O absorption [11], two bands at 1320 cm −1 and 860 cm −1 due to the absorptions of P– N(CH 3 ) 2 [12 ] and at 1710 (C O, ester). Moreover, the IR spectrum of oxazaphospholene product 7a re- vealed the absence of the absorption bands at 1580 (C N), 1660 (C O, Ar) and also the characteristic absorption band attributable to the stretching fre- quency of the enolate carbonyl function [13]. The 1 H NMR spectrum (in CDCl 3 ) of the adduct showed a doublet centered at δ = 2.65 ( J HP = 11.07 Hz) due to the 6H of the dimethylamino group, a singlet at 3.55 (s, 3H, COOCH 3 ), and a singlet at 6.45 (s, 1H, = CH COOCH 3 ). The aromatic protons appeared 511