Free and Metal‐Coordinated (N‐Isocyanimino)triphenylphosphorane: X‐ray Structures and Selected Reactions

Abstract

An improved procedure for the synthesis of (N-isocyanimino)-triphenylphosphorane, CϵN-N=PPh 3 (3), is described. The X-ray structure analysis reveals an unusually small N-N=P angle [115.2(2)°] and an N-N bond order of only about 1.5, which indicates considerable CϵN-N --P + participation and electronically more-isolated functional groups (CN, P=N) in the isocyanide than, for example, in the isomeric NϵC-N=PPh 3 (4) [C-N=P = 123.0(4)°, C-N bond order = 2.0]. In order to gain insight into the stereochemical consequences of metal coordination of 3, an X-ray structural study of [Cr-(CO) 5 CϵN-N=PPh 3 ] (5) was also undertaken. Surprisingly, the central bond lengths (C-N, N-N) and angles (C-N-N) remain practically unchanged with noticeable coordination effects occurring only at the periphery of 5, with the N-N-P angle [112.3(2)°] further decreased by 15σ, the elongated (by 7σ) P-N bond, the somewhat shortened (by 4σ) P-C(Ph) bonds and even shorter C-H(Ph) bonds on the one side, and the well-known Cr-C(O) trans contraction on the other. Treatment of 5 or its tungsten derivative with anhydrous Brønstedt and Lewis acids such as CF 3 COOH, HCl, COS, phosgene or,

One-pot, Three-component Synthesis of Fully Substituted 1,3,4-Oxadiazole Derivatives from (N-Isocyanoimino)triphenylphosphorane, Aromatic Carboxylic acids and (1R)-(-)-Campherchinon

“…22 Other starting materials and solvents were obtained from Merck (Germany) and Fluka (Switzerland) and were used without further purification. The methods used to follow the reactions are TLC and NMR.…”

“…Iminophosphoranes are important reagents in synthetic organic chemistry, especially in the synthesis of naturally occurring products, compounds with biological and pharmacological activity. 21,22 However, the organic chemistry of (N-isocyanimino)triphenylphosphorane 3 remains almost unexplored. (N-Isocyanimino)triphenylphosphorane 3 is expected to have synthetic potential because it provides a reaction system in which the iminophosphorane group can react with a reagent having a carbonyl functionality.…”

“…(N-Isocyanimino)triphenylphosphorane 3 is expected to have synthetic potential because it provides a reaction system in which the iminophosphorane group can react with a reagent having a carbonyl functionality. 21,22 In recent years, we have established a one-pot method for the synthesis of organophosphorus compounds. [23][24][25] In this paper, we report an interesting three-component reaction of (N-isocyanimino)triphenylphosphorane 3 (Scheme 1).…”

Four-Component Synthesis of 2-(N,N-Dialkylamino)-2,4,6-Cycloheptatrien-1-One Derivatives from Tropolone, an Isocyanide, a Primary Amine and an Aldehyde via Ugi-Smiles Coupling Reaction

“…[14][15][16][17][18][19][20] As part of our ongoing program to develop efficient and robust methods for the synthesis of heteroatom-containing compounds, [21][22][23][24][25][26] we sought to develop a convenient preparation of a new class of 2-(N,N-dialkylamino)-2,4,6-cycloheptatrien-1-one derivatives 5a-j by a novel four-component condensation reaction of aldehydes 1, primary amines 2, isocyanides 3 and tropolone 4 in fairly good yields (Scheme 1).…”

Preparation of Fully Substituted 1,3,4-Oxadiazole Derivatives from N-Isocyaniminotriphenylphosphorane, (E)-Cinnamic Acids, Chloroacetone and Primary Amines

“…N-isocyaniminotriphenylphosphorane 4 is expected to have synthetic potential because it provides a reaction system in which the iminophosphorane group can react with a reagent having a carbonyl functionality. 7,8 In recent years, we have established a one-pot method for the preparation of organophosphorus compounds.…”