Abstract
Treatment of the lithium 1-aza-allyl [Li{N(R)C(tBu)CHR}]21, abbreviated as [Li(LL′)]2, with PCl3 gave in poor yields the trans-P,P′-dichlorodiazaphosphetidine ClPN(R′)P(Cl)NR′ 3 (R=SiMe3, R′=C(tBu)C(H)SiMe3). An improved route to 3 was based on [{Cu(μ−LL′)}2] and PCl3. However, the method of choice involved conversion of 1 into successively the imine RNC(tBu)CHR24 (which upon heating gave the isomeric enamine 5) and Cl2PNC(tBu)CHR26 and thermolysis of 6. The imine RNC(tBu)CH(R)PPh27, obtained from [Li(LL′)]21 and Ph2PCl, was isomerised into the Z-enamine R2NC(tBu)C(H)PPh28, which upon irradiation gave a mixture of 8 and its E-isomer 9. Treatment of 7 with R″PCl2 or PCl3 gave the cyclic phosphonium chlorides [Ph2PP(R″)N(H)C(tBu)CH]Cl (10 R″=Ph, or 11 R″=Et) or [Ph2PP(Cl)N(R)C(tBu)CH]Cl 12; 12 with AgOSO2CF3 or Na[BPh4] afforded [Ph2PP(Cl)N(R)C(tBu)CH]A (13 A=CF3SO3, or 14 A=BPh4). The enamines RNC(tBu)CH(X)R (15 X=Cl, or 16 X=I) were obtained from 1 and POCl3 or ICl, respectively, and the enamine R2NC(Ph)CR217 was obtained from the lithium 1-aza-allyl [Li{N(R)C(Ph)CR2}(THF)] and CF3SO3SiMe3. Compounds 3–17 were characterised by multinuclear NMR spectroscopy and (in most cases) MS, while single crystal X-ray diffraction data are provided for 3 and 10.
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