Heterocycles Incorporating a Pentacoordinated, Hypervalent Phosphorus Atom

The SN2 reaction and its relationship with the Walden inversion, the Finkelstein and Menshutkin reactions together with theoretical calculations for the Finkelstein reaction

“…This was well known for silicon [12,13], but with P + , this situation has not been reported before (the Menshutkin examples stop at the quaternary salt [25][26][27]). The transformation of tetravalent phosphonium salts into pentavalent phosphoranes (right side, bottom equation) is a common reaction in phosphorus chemistry [62,63]. The barrier for the S N 2@C is 43.7 kJ•mol -1 [64] and for S N 2@N + is 33.4 kJ•mol -1 ; thus, a moderate decrease of the barrier was calculated (10.3 kJ•mol -1 ).…”

Synthesis of Pentacoordinated Spiro[4.4]phosphoranes by Reaction of Cyclic Phosphazenyl Anions with Epoxides: Study of their P-Remote Functionalization and Hydrolysis

“…5(3) in the basal plane and 85.0(3) -92.9(2) between basal and apical positions. 1,12,17 Phosphazenes 14a,b monosubstituted at carbon  to the phosphorus provided the spirophosphoranes 17e,f in the reaction with 2,2-dimethyloxirane, respectively, in high NMR yields (92-93%) and with improved diastereoselectivity in favour of the cis isomer, in which [1,2] steric interactions with the rigid benzoazaphospholone moiety and the substituent at carbon C3 are minimized. Compounds 17e,f undergo easily hydrolysis and they were characterized from the crude reaction mixture without further purification.…”

“…14 Higher stability of pentacoodinated spirophosphoranes is provided by the Martin ligand 15 (ML in compound 3, Figure 1) and its derivatives 16 due to the higher ability of the fluoroalkoxy moiety of ML for accumulating the negative charge developed at the apical position of a trigonal bipyramide (tbp) as compared with the sp 2 hybridized carbon of ooBP. 1,12,17 Spiro[4,4]phosphoranes 3 bearing two ML units have been extensively investigated in terms of fluxionality 17b and reactivity. The synthetic applications of compounds 3 are based on reactions at the phosphorus center with nucleophiles 18 and electrophiles (after P-H deprotonation) 19 including epoxides, 20 and at the carbon 12,17,21 or nitrogen atom 22 adjacent to the phosphorus after proton abstraction with a strong base (Figure 1).…”

“…1,12,17 Spiro[4,4]phosphoranes 3 bearing two ML units have been extensively investigated in terms of fluxionality 17b and reactivity. The synthetic applications of compounds 3 are based on reactions at the phosphorus center with nucleophiles 18 and electrophiles (after P-H deprotonation) 19 including epoxides, 20 and at the carbon 12,17,21 or nitrogen atom 22 adjacent to the phosphorus after proton abstraction with a strong base (Figure 1). Interestingly, the protic solvent mediated or acid catalyzed hydrolysis of spiro [4,4] We have reported that (N-methoxycarbonyl)phosphazenes 4 are useful reagents for the stereoselective synthesis of di-triand tetra-substituted alkenes 5 via C  monolithiation (Scheme 1, route a) 24 or C  ,Cortho dianions 7 (route b).…”

“…A successful strategy for accessing stable hypervalent phosphoranes consists of constructing spirane systems by binding two bidentate ligands to a phosphorus spiro atom. 12 Hellwinkel introduced in 1965 the o , o ′-biphenyl ( oo BP) ligand for the preparation of spirobi(benzophosphindoles) 13 1 (Figure 1 ) and Vedejs and co-workers used this approach for the synthesis and identification through solution NMR spectroscopy of elusive spiro-1,2-oxaphosphetanes formed in the course of Wittig reactions including derivatives of semi-stabilized phosphorus ylides 2 . 14 Higher stability of pentacoordinated spirophosphoranes is provided by the Martin ligand 15 (ML in compound 3 , Figure 1 ) and its derivatives 16 due to the higher ability of the fluoroalkoxy moiety of the ML for accumulating the negative charge developed at the apical position of a trigonal bipyramid (tbp) as compared with the sp 2 hybridized carbon of oo BP.…”