Synthesis of 2H-Azirine by [1+2]-Cycloaddition of a Phosphinocarbene with a Nitrile and its Ring-Expansion to 1,2 lambda 5-Azaphosphete
Résumé
mation of the (Z) isomer supports the assumption that in compound 13 (and probably also in 12) the substituents at the noncoordinated C=C double bond are arranged cis. The rhodium-containing product of the reaction of 8 or 13 with acetic acid is the chelate complex 17,[*] which can be reconverted in two steps [a) reaction with HC=CR to give I;14b1 b) "chromatography" of I on chloride-containing A1,0,[' 31] to the starting materials 2 and 3. In this way a cyclic process can be established by which, from HC=CR, RMgX, and CH,CO,H and assisted by the metal, an olefin RCH=CHR' (R = Ph, t B u ; R = Me, CH=CH,) is regio-and stereoselectively formed. trans-[RhH(C=CR)($-O2CCH3)(PiPr,),l I Preliminary attempts indicate that the "metallabutatrienes" J[14] behave similarly towards Grignard reagents as the vinylidene complexes 1-3 and that the corresponding vinyl metal derivatives K undergo isomerization reactions as well. Therefore, the expectation is that even higher unsaturated hydrocarbons than 18 could be accessible by a rhodium-assisted CC coupling procedure.