Phosphirenes and Diphosphetenes: the Products of the Reaction of A3-lminophosphineswith 1 -Alkoxy- and 1 -Aminoalkynes Aiexei D. Averin, Nikolai V. Lukashev; Marina A. Kazankova and irina P. Beietskaya Department of Chemistry, M. V. Lomonosov Moscow State University, 117899 Moscow, Russian Federation. Fax: + 7 095 939 0 156 The reaction path in cycloaddition reactions of A3-iminophosphineswith alkoxy- and amino-alkynes depends on the type of starting compound and solvents employed and leads to the formation of phosphirenes or 1,2-diphosphetenes. Work by S~hoeller'.~ and Nie~ke~.~ provides evidence that cycloaddition reactions of A3-iminophosphines with double and triple bonds can result in products of [2 + 21- and [2 + 11- cycloaddition that are dependent on the type of substituent in the A3-iminophosphine. Using tolan (diphenylacetylene) and tert-butylphosphaalkyne the corresponding A5-phosphirene3 and hS-diphosphirenes4 were obtained. Here we report on the influence of the type of alkyne, A3-iminophosphine and solvent used upon the reaction path of cycloaddition. The reactions of dilute solutions of A3-iminophosphines 1 in pentane with alkylalkoxyalkynes 2 give the corresponding ", ,,r" RlP=NAr + R2CfCOR3 - L \ (1) 1 2 R2 /C-C\ORB Ar = 2,4,Mrktert-butylphenyl 3a-9 3a: R' E ~h, R2 = R3 = ~e 3b: R' = But, F? = Et. R3 = Me 3c: R' = But, R2 = P~;P, R3 = Et 3d: R' = But, R2 = Me3Si, R3 = Et 3e: R' = BU', R2 = Me3Ge, R3 = Et 3f: R' = CI, F12 = Et, = Me 39: R' = Ph, R2 = prZ1p. R3 = Et Mendeleev Commun., 1993, 3(2), 68–70 Mendeleev Communications