Cyclodiphosph(III)azane chemistry – Ylides from the reaction of [(RNH)P-N(t-Bu)]2 [R = t-Bu, i-Pr] with dimethyl maleate and chiral ansa-type derivatives from reaction of [ClP-N(t-Bu)]2 with a substituted BINOL

Use of a simple inorganic ring system with the cyclodiphosph(III)azane skeleton [e.g. [(RNH)P-N(t-Bu)]2 [R = t-Bu (7), i-Pr (8)] to probe some of the intermediates proposed in phosphine mediated organic reactions is highlighted. Thus the reaction of 7–8 with the allenylphosphine oxide Ph2P(O)C(Ph)CCH2 (9) affords the phosphinimines [(RNH)P(μ-N-t-Bu)2P(N-R)-C(CH2)CH(Ph)-P(O)Ph2] [R = t-Bu (10), i-Pr (11)], while a similar reaction of 7–8 with dimethyl maleate (or dimethyl fumarate) affords the ylides [(RNH)P(μ-N-t-Bu)2P(NH-R)C(CO2Me)-CH2(CO2Me) [R = t-Bu (18), i-Pr (19)]. The implication of such reactions on phosphine mediated organic transformations including Morita–Baylis–Hillman reaction is mentioned. In a rather rare type of situation, an unusually long phosphoryl (PO) bond [1.538 (5) Å] as revealed the X-ray structure of {(R)-6,6′-(t-Bu)2-1,1′-(C10H5)2-2,2′-O2-}{P(O)(N-t-Bu)2-P(Se)} (27) is rationalized by means of crystallographic disorder in packing after comparing the data with that in the literature and {1,1′-(C10H6)2-2,2′-O2}{P(Se)(N-t-Bu)2-P(Se)} (29). X-ray structures of the new compounds 10–11, 18–19, 27 and 29 are discussed. Compound 10 crystallizes in the chiral space group Pca2(1) with (S)-chirality at the carbon center [–C(CH2)CH(Ph)-P] suggesting a case of spontaneous resolution through crystallization.

Graphical abstractFormation of a phosphinimine or an ylide in the reaction of cyclodiphosphazanes of type [(RNH)P-N(t-Bu)]2 with allenylphosphine oxide Ph2P(O)C(Ph)CCH2 or dimethyl maleate is highlighted. Ansa-type cyclodiphosphazane with a chiral BINOL residue and an unusually long phosphoryl (PO) bond in one such compound is described.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► The reaction of [(RNH)P-N(t-Bu)]2 with Ph2P(O)C(Ph)=C=CH2 affords phosphinimines. ► A similar reaction of [(RNH)P-N(t-Bu)]2 with dimethyl maleate affords ylides. ► These results have implications for the Morita-Baylis-Hillman reaction. ► A long P=O bond [1.538(5) Å] is revealed in the X-ray structure of compound 27. ► Compound 10 crystallizes in the chiral space group Pca2(1).