Portal de Periódicos da CAPES

Oxygen-atom transfer from nitrous oxide (NNO) to nickel alkyls. Syntheses and reactions of nickel(II) alkoxides

1995; Elsevier BV; Volume: 14; Issue: 1 Linguagem: Inglês

10.1016/0277-5387(94)00330-h

1873-3719

Phillip T. Matsunaga, John C. Mavropoulos, Gregory L. Hillhouse,

Oxidative Organic Chemistry Reactions

The dialkyl nickel complexes (bipy)Ni(R)2)(1 R Et; 2, R  iso-Bu; bipy  2,2′-bpyridine) react with nitrous oxide (1 atm) to generate nickel(II) alkoxy alkyl complexes (bipy)Ni(OR)(R) (3, R  Et; 4, R  iso-Bu), which in turn undergo CO-insertion followed by reductive elimination under a carbon monoxide atmosphere to afford the corresponding esters (ethyl propionate from 3; 2-methylbutanoic acid-2-methylpropyl ester from 4). Nitrous oxide reacts with the metallacyclopentane complex (bipy)Ni{(CH2)4} (5) to give the oxametallacycle (bipy)Ni{O(CH2)3CH2} (6) and with (phen) Ni{(CH2)4} (7; phen  1,10-phenanthroline) to give (phen) Ni{O(CH2)3CH2} (8). Complex 6 undergoes elimination reactions with HCl to give 1-butanol, with I2 to give tetrahydrofuran, and with CO to give δ-valerolactone. The α-methyl substituted metallacycle (bipy)Ni {(CH2)3CHCH3} (9) reacts with N2O in a regioselective fashion (at the more highly substituted NiC bond) to give (bipy) Ni{OCH(CH3)CH2CH2CH2} (10) exclusively. Complex 10 undergoes elimination reactions with HCl to give 2-pentanol, with I2 to give 2-methyl-tetrahydrofuran, and with CO to give δ-caprolactone. The β,β′-dimethyl substituted metallacycles, meso-(bipy)Ni{CH2CH(CH3)CH(CH3)CH2} (11) and d,l-(bipy)Ni{CH2CH (CH3)CH(CH3)CH2} (12) react with N2O to produce the oxametallacycles (bipy)Ni{cis-OCH2CH(CH3)CH(CH3)CH2}(13) and (bipy)Ni{trans-OCH2CH(CH3)CH(CH3)CH2} (14), respectively. Complex 13 undergoes elimination reactions with HCl to give 2,3-dimethyl-l-butanol, with I2 to give cis-3,4-dimethyl-tetrahydrofuran, and with CO to give tetrahydro-cis-4,5-dimethyl-2H-pyran-2-one. The metallacycles (bipy)Ni{CH2C(CH2)C(CH2)CH2} (15) and (bipy)Ni{(CH2)2C6H4} (16), both possessing sp2-hybridized ring carbons in the β- and β′-positions, show no reactivity toward N2O. However, 16 reacts with HCl to afford o-xylene, with CH2Br2 to afford indan, and with maleic anhydride to afford tetrahydronaphthalene anhydride.