1,3-Dipolar Cycloaddition of Nitrones to Gold(III)-Bound Isocyanides

Abstract

Treatment of gold(III)-isocyanides [AuCl3(CNR1)] (R1 = Xyl 1, Cy 2, But 3) with an equimolar amount of 5,5-dimethyl-1-pyrroline-N-oxide (4) in CH2Cl2 at −74 °C leads to the generation of the heterocyclic aminocarbene species [AuCl3{C(ONaCMe2CH2CH2CbH)═NeR1}(Na–Cb)(Cb–Ne)] 8 (for R1 = But) or gold(III) complexes cis-[AuCl2{Na(CMe2CH2CH2CbNeR1)Cd═O}(Na═Cb)(Ne–Cd)] 9 and 10 (for R1 = Xyl and Cy) in good isolated yields (75–87%). DFT calculations show that deprotonation of the endocyclic CH group in the carbene ligand leads to spontaneous N–O bond cleavage, and acidity of this group is a factor controlling the different chemical behavior of 1–3 depending on the nature of substituent R1. The reaction of equimolar amounts of the aldonitrone p-TolCH═N+(Me)O– (5) or the ketonitrones Ph2C═N+(R2)O– (R2 = Ph 6, CH2Ph 7) with 1–3 in CD2Cl2 at −70 °C in air (or under N2) revealed the formation of the carbene complexes [AuCl3{C(ONMeCaH-p-Tol)═NbR1}(Ca–Nb)] (R1 = Cy 11, Xyl 12, But 13), [AuCl3{C(ONPhCaPh2)═NbR1}(Ca–Nb)]...