Crystal structure, theoretical study and mechanism investigation of stable phosphorus ylide involving 9-carbazole

The crystal structure of di-tert-butyl 2-(9H-carbazol-9-yl)-3-(triphenylphosphoranylidene) butanediate has been determined by X-ray crystallography. This compound crystallizes in a monoclinic space group P21/n with cell parameters a = 17.566(3) ?, b = 12.2342(9) ?, c = 18.5561(12) ?, B = 117.818(12)°, V = 3527.0(7) ?3, Dcalc = 1.235 mg m-3, and Z = 4. The final R value is 0.0463 for 12602 reflections. Mechanistic investigation of the reaction between di-tert-butyl acetylenedicarboxylate and triphenylphosphine in the presence of 9-carbazol as a N-H heterocyclic compound was fully discussed. In addition assignment of the stability of the two Z- and E- isomers of ylide involving 9-carbazole have been performed using quantum mechanical calculations.