Quinones, formation from alkynes

The CDC between A-f-butyl nitrones and terminal alkynes to form alkynylated nitrones in good to excellent yields, catalysed by zinc trifiate, was achieved using 3,3, 5,5 -tetra-tertbutyldipheno-quinone and O2 as oxidants. The alkynylated nitrones were transformed to regioisomerically pure 3,5-disubstituted isoxazoles. Experimental and DFT computational studies of Pd(OAc)2/pyridine-catalysed intramolecular aerobic oxidative amination of alkenes supported a stepwise mechanism that involved (i) the formation of a Pd(ll)-amidate-alkene chelate with release of 1 equiv. of pyridine and AcOH from the catalyst centre, (ii) insertion of alkene into a Pd—N bond. 

Yellow complexes of formula RC2R Fe(CO) have been obtained from Me CCesCCMe, Me SiCsCSiMe and PhCsCSiMe, and are regarded as alkyne substituted, pentacarbonyliron compounds for which a structure analogous to acrylonitrile Fe(CO) (4) has been adopted. Their further reaction with other alkynes at room temperature leads to complexes of types (RC Rj COFe CCO), (RC Rl Fe fCO), and (RC2R) Fe2(CO)g and is discussed together with their role in the formation of quinones. 

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