Electron impact induced fragmentations and rearrangements of aliphatic, heterocyclic phosphine oxides

Abstract

A. A solution of 1.4 g (0.026 mol) of pr~piolaldehyde~~ and 1.8 g (0.026 mol) of isoprene was kept neat at room temperature for 70 h. Distillation of the reaction mixture yielded 2.0 g (63%) of 35, bp 84-87 O C (10 Torr) [lit.23 bp 95.5-96 OC (20 Torr)].Method B. A solution of 2.8 g (0.052 mol) of8 and 3.6 g (0.053 mol) of isoprene in 100 ml of Et20 was kept at room temperature for 70 h. The volatiles were removed in vacuo and the residue weighing 0.34 g was distilled to give 0.14 g of 35, bp 84-86 "C (11 Torr) [lit.23 bp 95.5-96 O C (20 Torr)]. In the case of some isomeric 2-methyl-I ,3-butadien-l-ylphosphonates the lower field absorption of the y proton in the cis isomer has been attributed to hydrogen bond formation between the phosphonyl oxygen and the proton:Common electron impact induced fragmentations and rearrangements of 1-ethylphospholane 1-oxide (l), 1ethylphosphorinane 1-oxide (2), l-phosphabicyclo[2.2.l]heptane 1-oxide (3), and 1-phosphabicyclo[2.2.2]octane 1-oxide (4) were investigated, and the nature of the fragments were compared with those resulting from similar decompositions of trimethylphosphine oxide (5), triethylphosphine oxide (6), quinuclidine (7), and quinuclidine Noxide (8). Details of ethylene loss from and concomitant rearrangement of 1 were investigated using specifically deuterium-labeled derivatives. Possible structures for some of the major fragments and rearrangement products are proposed.