ChemInform Abstract: The Reaction of Ethyldichlorophosphine with N,N‐Dibutyl‐2,3‐butanediimine.

Abstract

248ChemInform Abstract The diimine (I) reacts with ethanephosphonous acid dichloride (II) to produce the phosphonium salt (III). (1H-, 31P-NMR-, IR-data).

Recent Developments in the Chemistry of N-Heterocyclic Phosphines

“…Even though interpretation of the data using quantitative structure correlation was not possible [55] , it has been suggested that increasing bond length [33] a Anions 8 , 9 b Structures containing both isolated and benzannulated rings c For report of an exceptionally short P-N bond outside the usual range cf. [72] alternation is associated with a general deterioration of cyclic p -electron delocalization [8,18,39] . The structures of P-chloro-NHPs invited attention due to the very early discovery of species with exceptionally long P-Cl bonds [19,22,53] which stimulated discussions about a possible ionic nature of these compounds.…”

“…Hydrolysis at ambient temperature may be unselective and 3 Condensation to yield the secondary product is often favored when solutions of NHPs are exposed to moist air or solvents and may result in formation of a mixture of 17 and 18 . proceed often via ring cleavage [38] . Owing to the ionic polarization of P-H or P-P bonds (see Sect.…”

“…In all cases, care has to be taken to avoid overreduction causing P-N bond cleavage. Introduction of P-alkoxy and P-amino substituents is feasible by reaction of the P-chloro-derivatives with either an alcohol or NH-functional amine in the presence of triethylamine as acid scavenger, or by metathesis with a suitable alkoxide or amide, respectively [38,42] . Thus, reactions of P-chloro-NHPs with sodium amide in liquid ammonia were reported to yield either a P-amino-1,3,2-diazaphospholene 16 with an unsupported NH 2 -group, or an iminobis(diazaphospholene) 17 (Scheme 6 ) [42] .…”

“…C-Substitution reactions were studied in the case of the difunctional 1,3-dicyclohexyl-2,4-dichloro-1,3, 2-diazaphospholene 9 (Scheme 3 , R 1 = Cy) which was found to display a diverse reactivity [38] . Thus, soft nucleophiles (triethyl phosphite, tributylphosphine) seem to react preferably under replacement of the C-chloro-substituent to give 4-phosphoryl-or phosphonio-derivatives whereas hard nucleophiles (EtOH) attack first the P-Cl and then the C-Cl functionality, and reactions with electrophiles (SbCl 5 , MeI) proceed specifically via abstraction of P-Cl substituent to give 1,3,2-diazaphospholenium salts.…”

“…The observed reactivity matches the typical behavior of all halogen-substituted phosphines. Halogen exchange reactions were carried out by treating P-chloro-NHPs with alkyl [38,40] or trimethylsilyl halides [20,41] which allowed replacement of a halogen atom by a heavier congener (i.e., substitution of Cl by Br, I, and of Br by I); fluoro-substituents may be introduced by reaction with silver fluoride [20] . A pyrido-annulated P-iodo-NHP was also obtained by reduction of a ionic diazaphospholenium triiodide with potassium [33] .…”