Methylene‐Azaphosphirane as a Reactive Intermediate

Abstract

Reaction of the transient phosphinidene complexes R‐PW(CO)5 with N‐substituted‐diphenylketenimines leads unexpectedly to the novel 2‐aminophosphindoles, as confirmed by an X‐ray crystal structure determined for one of the derivatives. Experimental evidence for a methylene‐azaphosphirane intermediate was found by using the iron‐complexed phosphinidene iPr2N‐PFe(CO)4, which affords the 2‐aminophosphindole together with the novel methylene‐2,3‐dihydro‐1H‐benzo[1,3]azaphosphole. Analysis of the reaction pathways with DFT indicates that the initially formed methylene‐azaphosphirane yields both phosphorus heterocycles by way of a [1,5]‐ or [1,3]‐sigmatropic shift, respectively, followed by a H‐shift. Strain underlies both rearrangements, which causes these remarkably selective conversions that can be tuned by changing the substituents.

Alkyne Insertion into P–C(sp2) Bonds as a Route to Fused Phospholes: Transition-Metal-Like Reactivity at Phosphorus

“…The P−C distance of 1.839(2) on the alkene side of the phosphole ring is consistent with those reported for W coordinated benzophosphole rings; however, the P−C bond distance on the ring-fused side (1.786(2) Å) is significantly shorter than those in benzophosphole rings. 10,12,17,28 In contrast to the phosphole ring, the pyrrole ring is clearly aromatic. This is evident from the ring planarity (mean deviation of atoms from plane = 0.002 Å), the planarity of the N atom (sum of angles = 359.7°), and the bond lengths within the ring.…”

Diastereoselective Formation of Complexed Methylenediphosphiranes

“…The first step in the reaction is likely to be the addition of [R−PW(CO) 5 ] to the phosphorus lone pair of 8 ′, resulting in syn and anti P,P-ylides 10 ′ , as the initial (kinetic) products ( syn - 10a ′, Δ E = −15.4; anti - 10a ′, −15.1 kcal·mol −1 ; Figure , all energies are relative to syn - 10a ′) in analogy to the formation of the well-documented P,N-ylides. , Due to the small energy difference between syn and anti P,P-ylides 10 ′ (Δ E = 10a ′, 0.3; 10b ′, 0.7 kcal·mol −1 ), they will readily interconvert via a simple rotation around the P1−P2 bond, of which the clockwise motion ( TS2 ; Δ E ⧧ = 10a ′, 2.6; 10b ′, 2.3 kcal·mol −1 ) is favored over the counter-clockwise motion ( TS1 ; Δ E ⧧ = 10a ′, 5.2; 10b ′, 4.3 kcal·mol −1 ; Figure ).…”

“…Heteroallenes are especially interesting because of their accessibility and reactivity . For example, ketenimines (RNCCR 2 ) react with phosphinidene complexes [R−PML n ] (ML n = W(CO) 5 and Fe(CO) 4 ) to give methylene-azaphosphiranes 4 , which undergo a [1,5]-sigmatropic rearrangement and a H-shift to afford 2-aminophosphindoles 5 …”

Nitrogen, phosphorus, arsenic, antimony and bismuth

“…51 Although the compound is quite thermally stable, Scheme 2 heating to 130 1C (Scheme 4) results in the formation of the two species 21 and 22 (in the case where R = Me): the isomerisation to 21 is thought to proceed via a 1phosphabutadiene. Phosphinidene ligands have also been shown to be converted into Z 1 -phosphaalkene and Z 1 -coordinated diazaphosphaallene ligands, 52 to act as precursors for 2-aminophosphindole, 53 phospha[n]triangulanes 54 and substituted phosphiranes, 55,56 An example of an in situ generation of the fluoro-substituted phosphinidene complex [FP-Mo(CO) 5 ] has been reported which may be trapped by Ph 2 C 2 and 2-dimethylbutadiene. 57 The reaction of a phosphinidene, which is stable at room temperature, with MeOTF results in a remarkable dimerisation reaction to give the bowl-shaped molecule 23 (Scheme 5).…”