RESUMO
[reaction: see text] The synthesis of an advanced intermediate in the synthesis of the title compound has been achieved. Key steps include an Ireland-Claisen rearrangement to install the C7 tertiary alcohol stereocenter, an SN2' reaction of an alkoxymethyl Cu reagent, and a diastereoselective Re-catalyzed allylic alcohol transposition.
Assuntos
Hidrocarbonetos Aromáticos com Pontes/síntese química , Diterpenos/síntese química , Furanos/síntese química , Hidrocarbonetos Aromáticos com Pontes/química , Catálise , Cobre/química , Ciclização , Diterpenos/química , Furanos/química , Estrutura MolecularRESUMO
Reaction of isopropyl[(2-pyridyl)alkyl]amines such as N-isopropyl-N-2-methylpyridine or N-isopropyl-N-2-ethylpyridine with aqueous solutions of NaAuCl(4) led to the formation of [LAuCl(2)][AuCl(4)] in low yields, where L = pyridyl amine bound to gold in a bidentate fashion. Reaction of 2-(3,5-diphenyl-1H-pyrrol-2-yl)pyridine with aqueous NaAuCl(4), however, proceeded with formal loss of HCl and direct formation of the gold(III) amido complex L'AuCl(2), where L' = deprotonated pyrrolyl ligand. Optimization of the reaction conditions to make the new amido complex identified MeCN:H(2)O (1:2) as the best choice of solvent, affording product in 92 % yield. This dichloro amido complex is a convenient precursor to L'AuMe(2), which was found to be air-stable and thermally robust.
RESUMO
The use of tpy'(tpy'= 4,4',4''-tri-tert-butyl-terpyridine) as a ligand for nickel allows for the isolation of a Ni(I)-alkyl complex and a Ni(II)-alkyl halide complex, both of which can be used as mechanistic probes of key steps in alkyl cross-coupling reactions.
Assuntos
Reagentes de Ligações Cruzadas/química , Hidrocarbonetos Halogenados/química , Níquel/química , Compostos Organometálicos/química , Piridinas/química , Catálise , Modelos Moleculares , Estrutura Molecular , OxirreduçãoRESUMO
The ability of the terpyridine ligand to stabilize alkyl complexes of nickel has been central in obtaining a fundamental understanding of the key processes involved in alkyl-alkyl cross-coupling reactions. Here, mechanistic studies using isotopically labeled (TMEDA)NiMe(2) (TMEDA = N,N,N',N'-tetramethylethylenediamine) have shown that an important catalyst in alkyl-alkyl cross-coupling reactions, (tpy')NiMe (2b, tpy' = 4,4',4' '-tri-tert-butylterpyridine), is not produced via a mechanism that involves the formation of methyl radicals. Instead, it is proposed that (terpyridine)NiMe complexes arise via a comproportionation reaction between a Ni(II)-dimethyl species and a Ni(0) fragment in solution upon addition of a terpyridine ligand to (TMEDA)NiMe(2). EPR and DFT studies on the paramagnetic (terpyridine)NiMe (2a) both suggest that the unpaired electron resides heavily on the terpyridine ligand and that the proper electronic description of this nickel complex is a Ni(II)-methyl cation bound to a reduced terpyridine ligand. Thus, an important consequence of these results is that alkyl halide reduction by (terpyridine)NiR(alkyl) complexes appears to be substantially ligand based. A comprehensive survey investigating the catalytic reactivity of related ligand derivatives suggests that electronic factors only moderately influence reactivity in the terpyridine-based catalysis and that the most dramatic effects arise from steric and solubility factors.
Assuntos
Alcanos/síntese química , Piridinas/química , Alcanos/química , Catálise , Cristalografia por Raios X , Espectroscopia de Ressonância de Spin Eletrônica , Hidrocarbonetos Halogenados/química , Ligantes , Modelos Moleculares , Níquel/química , Compostos Organometálicos/química , Oxirredução , Espectrofotometria UltravioletaRESUMO
Addition of terpyridine to (TMEDA)Ni(CH3)2 results in the high-yield formation of (terpyridyl)NiMe (3). This NiI organometallic complex was found to be capable of transferring its methyl group to iodocyclohexane to produce methylcyclohexane in high yield. Compound 3 can also serve as an initiator for the catalytic cross-coupling of alkyl electrophiles performed under Negishi-like conditions.