Gas phase thermolysis of allylphosphines, kinetic study

Abstract

Diallylphenyl, allylbenzylphenyl and allylmethylphenyl phosphines were pyrolized in a stirred-flow reactor at 380-429"C/7-20 A six-center cyclic transition state unimolecular reaction mechanism, consistent with the aboue Arrhenius parameters, is proposed for the propene elimination reaction.

The Ene Reaction in the Chemistry of Low-Coordinate Phosphorus

“…In this case, propene elimination during flash vacuum thermolysis generates the parent 1-phosphabutadiene 16 (R = H), as well as derivatives bearing only a phosphorus substituent. [26][27][28][29] The highly reactive products 16 could be characterized by IR spectroscopy, MS and PES, as well as by chemical trapping when R = H, Me. 27 In the case of R = t-Bu, Ph, the 1phosphabutadienes 16 were observed by low-temperature 31 P NMR spectroscopy, and were isolated as diphosphacyclohexadiene isomers formed by dimerization in a [4+2] cycloaddition upon warming.…”

“…Thus, the phenylallylphosphines 13 eliminate propene by pyrolysis in a stirred-flow reactor, using toluene as the carrier gas, to form the P-phenylphosphaalkenes 14 (Scheme 8). 26 The product in the case of R = Ph could be characterized as 1,2-diphosphetane isomers formed in a head-to-head [2+2] cycloaddition, whereas the transient P-phenylphosphaethene (14, R = H) leads only to oligomers. Kinetic studies on these fragmentations (also for R = CH=CH 2 , Scheme 9) showed first-order kinetics consistent with a unimolecular reaction mechanism and a sixcenter cyclic transition state.…”

Reactivity of allylphosphines with iridium complexes: Diallylphosphines as new bidentate ligands

“…The use of stronger bases, such as DBU, t-BuOK, or lithium bistrimethylsilylamide, resulted in the formation of insoluble products that we were not able to characterize. This preliminary work shows the different reactivity of diallylphosphines toward [COE 2 [19], t-butyldiallylphosphine [10], and diisopropylamino-diallylphosphine [14].…”

“…We have reported on the thermal decomposition of allyl and diallylphosphines as a novel way to generate phosphalkene derivatives, via a retroene type of propene elimination involving a six-center transition state [10][11][12][13][14].…”

Transition structure for the retroene-type elimination reaction of propene from allylamines

“…generation of some carbon-heteroatom double bonds; among these can be cited C‫ס‬O [4][5][6], C‫ס‬S [7,8], C‫ס‬N [9][10][11][12], C‫ס‬Si [13,14], and recently, C‫ס‬P [15,16].…”