Intramolecular cyclization of ω‐haloalkylsubstituted thiophosphorylacetonitriles: Synthesis and stereochemistry of 3‐cyano‐2‐oxo‐1,2‐thiaphosphacyclanes

Abstract

Intramolecular S-alkylation in a seriesof -haloalkyl-substituted thiophosphorylacetonitriles 5-7 presents an effective synthetic route to the hitherto unknown 3-cyano-2-oxo-1,2-thiaphospholanes 14 and thiaphosphinanes 15. The compounds were obtained as a mixture of cis-and trans-isomers that were resolved to individual stereoisomers in most cases. For some of them, X-ray diffraction analysis has been performed. It was shown that 31 P NMR spectroscopy can be used to assign the stereochemistry of 3-cyano-2-oxo-1,2-thiaphosphacyclanes.

Novel functionalised P-ligands: advances and application

“…The cis-and trans-arrangements of the substituents was unambiguously confirmed by the X-ray data [9] and corresponded well to typical 1 H NMR spectroscopic analysis based on the deschielding effect of the P@O bond on all the kinds of protons situated in the cis-position to the P@O group according to [11]. Moreover, it was shown that a cis-isomer is characterized by a downfield chemical shift for 8 while for six-membered compounds 9 a downfield chemical shift in the 31 P NMR spectrum correspond to the trans disposition of the mentioned substituents [10]. The similar characteristic disposition of the signals in the 31 P NMR spectra was observed for cyano substituted cyclic compounds with tricoordinated phosphorus atom [12].…”

“…In the case of x-haloalkyl substituted thiophosphorylacetonitriles, such methodology gave rise to either mono or bicyclic cyanosubstituted thia- Scheme 2. phosphacyclanes (Scheme 3) [10]. Compounds 8a-c, 9a-g and 10 were formed as mixtures of R Ã P ; R Ã C -cis and R Ã P ; S Ã C -trans isomers differing in the mutual disposition of the phosphoryl oxygen atom and the cyano group in relation to the ring plane and separated by chromatography.…”

“…IR spectra were recorded in KBr pellets on a Fourier spectrometer ''Magna-IR750'' (Nicolet) with a resolution of 2 cm À1 after 128 scans. The starting phosphine oxides 1a-c [3][4][5], 4 [8], 8c, 9f [10], 14a-c, 15a-d, 16a-d [20] used as precursors for the ligands were obtained as described earlier. All the phosphines obtained had the purity >97% according NMR spectral analysis and were used in the subsequent complex formation without further purification.…”

Synthesis, some properties and structural features of 1,2-thiaphosphacyclanes

“…To obtain 2-oxo-1,2l 5 -(87, 88) or 2-oxo-1,2l 5 -thiaphosphacyclanes (89,90), one may use an intramolecular alkylation of o-chloroalkylphosphinous (91, 92) and -thiophosphinous acids occurring in the presence of triethylamine. 76,77 Virtually no side products are formed during this cyclisation and the reaction kinetics is approximately first order.…”

“…Thus if non-functionalised o-iodoalkylphosphine sulfides 105 undergo cyclisation in status nascendi under the action of NaI on chloro derivatives 104, the cyanosubstituted analogues 113 cyclise very slowly and in the equilibrium position the proportion of the corresponding phosphacyclanium salt 114 does not exceed 15%. 89 However, the a-CN group favours subsequent dealkylation in the phosphacyclanium salts formed (the intramolecular thione ± thiol rearrangement) with at least one alkoxy substituent at the phosphorus atom. Thus, o-chloroalkyl derivatives 115a,b undergo cyclisation to the 3-cyano-2-oxo-1,2-thiaphosphacyclanes 116a,b upon distillation in vacuo.…”