Phosphorus compounds, reactions with hexafluoroacetone

Further contributions to the study of the interaction of trico-ordinated phosphorus compounds with carbonyl compounds have been reported by Pudovic et al. In the first of these,a phosphoroisocyanitidite (83) reacts with the two moles of hexafluoroacetone (46) in ether at -25° to form the bicyclic phosphorane (85) via the ylid intermediate (84). Similar reactions occur with alkyltrifluoropyruvates ( CF3CO.CO2R, Me or Et) as substrates. In the second paper, the reaction of dimethyl alkynylphosphonites (86) with... 

Schmutzler et al. have also shown that chloromethyl dichlorophosphine (68) reacts with the bis(trimethylsilyl)urea (69) to form the a cr -diphosphorus compound 70. Subsequent reaction of 70 with hexafluoroacetone (71) resulted in an unusual rupture of the P-P bond to form 75 and the spirophosphorane 76 via 12-1 A. Another unusual reaction of 77 with 78 gave the spirophosphorane 79 and X-ray crystal structures of 76 and 79 showed a large deviation from both the idealised coordination geometries at phosphorus. ... 

At the same time, stable oxazaphospholenes 15 are formed by reactions of hexafluoroacetone N-acylimines 14 with chlorine-containing compounds of trivalent phosphorus (92JFC(58)345, 91DOK619, 92JFC(58)375, 95IZV1809, 89IZV1213, 91IZV239) (Scheme 17). 

In a short review of compounds containing the P-CH2-P fragment, Shevchenko et al. mention the reaction of (69) with alkyl isocyanates, azides" and hexafluoroacetone," all of which give penta- or hexa-coordinate phosphorus compounds. (e.g.70). An unusual reaction of (71) with (72) gave a similar zwitterionic structure (73). ... 

Studies on the synthesis of cage-like phosphoranes based on casade reactions of trivalent phosphorus derivatives with unsaturated activated compounds has continued. For example, reactions of phosphites bearing dioxaphosphorinane (1), dioxaphospholane (2) and catechol derivatives (3) with hexafluoroacetone, chloral, mesoxalic and trifluoropyruvic acid esters have been performed to produce a series of novel carcass -type pentacoordinated phosphoranes with high regio- and stereoselectivity. Hence, upon treatment of hexafluoroacetone (4) with phosphites (1) and (2), pen-taoxophosphoranes (5) and (6) were formed (Scheme 1). 

Hexafluoroacetone azine accepts nucleophiles (ROH, RSH, R NH) in positions 1 and 2 to yield hydrazones [27] Phosphites give open-chain products via a skeletal rearrangement [22] Radical addition reactions are also reported [22] Treatment of tnfluoropyruvates with tosylhydrazine and phosphorus oxychlo-ride-pyndme yields tnfluoromethyl-substituted diazo compounds [24] (equation 3)... 

The transformation of 4,4-difluoro-3-trifluoromethylbut-3-ene-l-ones 53, easily prepared from hexafluoroacetone (HFA), into 2-fluoro-3-trifluoromethylthio-phenes 54 proceeded on heating with phosphorus pentasulflde [32]. Yields of 2-fluoro-3-trifluoromethylthiophenes 54 depend on the reaction conditions and the progress of the transformation should be monitored by T NMR spectroscopy. The starting compounds were formed by elimination of water from hexafluoroacetone aldols 51 obtained by reaction of HFA with enol silyl ethers in the presence of Lewis acid such as SnCU. The unsaturated ketones 52 were reduced with SnCla and 53 were cyclized to the desired thiophenes 54 with phosphorus pentasulflde [33]. 

Treatment of perfluoroisopropylamine with sulphur tetrafluoride in the presence of caesium fluoride at 90 °C yields the iminosulphur difluoride (CFslaCF-NiSFa, which can also be prepared from hexafluoroacetone imine and sulphur tetrafluoride. Treatment of (21) with sulphur tetrafluoride in the presence of caesium fluoride at 70 °C yields the iminosulphur difluorides (CFa)aCF-N SFa, (CFa)aaN SFa)a, and (CFa)2(FaS N)C-N S N-C(N SF,)-(CFala, while with phosphorus pentachloride at 0 C it yields the iminosulphur dichloride (CFa)aCCl-N SCla. Similarly, treatment of the trifluoroacetyl compound CFa-CO-N iSFa (formed, together with CaFj-N SFa and CFg-COF by reaction of trifluoroacetamide with sulphur tetrafluoride in the presence of sodium fluoride at 90 °C) with phosphorus pentachloride gives CFa CO N SClj. Treatment of hexafluoroacetone hydrazone with sulphur tetrafluoride in the presence of caesium fluoride at 0— 20 C yields... 

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