Regioselectivity in the Cu(I)-Catalyzed [4 + 2]-Cycloaddition of 2-Nitrosopyridine with Unsymmetrical Dienes was written by Tran, Anh T.;Liu, Peng;Houk, K. N.;Nicholas, Kenneth M.. And the article was included in Journal of Organic Chemistry in 2014.Synthetic Route of C9H8N2O This article mentions the following:
The thermal (uncatalyzed) and Cu(I)-catalyzed reactions of 2-nitrosopyridine (PyrNO) with the dienes 1,3-pentadiene, E,E-2,4-hexadienol, and 1-phenylbutadiene are studied exptl. and computationally. The uncatalyzed reactions of the first two dienes occur with low regioselectivity, while the latter proceeds with complete proximal selectivity. Using the M06/6-311+G(d,p)-SDD method, various concerted transition states for the reactions of 2-nitrosopyridine with (E)-1,3-pentadiene and 1-phenylbutadiene were computed. In quant. agreement with the exptl. findings, (a) no energy difference (0.0 kcal/mol) is found between the most stable transition states, endo-prox-anti and endo-dist-anti, in the pentadiene/PyrNO reaction, leading to nearly equal amounts of prox and dist cycloadducts, and (b) the proximal transition state is strongly favored (by 3.7 kcal/mol) over the distal for the highly selective phenylbutadiene/PyrNO reaction. The regioselectivity of the pentadiene/PyrNO reaction is improved markedly (90:10 dist/prox) when catalyzed by Cu(CH3CN)4+; (diimine)2Cu+ catalysts increase selectivity for the proximal product (55-65%). Modest effects of the catalyst nature on regioselectivity are observed in the sorbyl alc. and 1-phenylbutadiene reactions. The relative affinity of an equilibrating set of (diimine)2Cu+ complexes for the prox and dist cycloadducts, assessed by ESI-MS, is marginally correlated with the prox/dist product regioselectivity produced by the corresponding catalysts. Transition states in the Cu(CH3CN)4+– and Cu(diimine)2+-catalyzed reactions are located that account for the observed regioselectivities. Coordination effects on the regioselectivity are derived from FMO orbital interactions and the extent of electron transfer between the Cu center and the coordinated nitroso and diene units. In the experiment, the researchers used many compounds, for example, 1-Methyl-1H-benzo[d]imidazole-2-carbaldehyde (cas: 3012-80-4Synthetic Route of C9H8N2O).
1-Methyl-1H-benzo[d]imidazole-2-carbaldehyde (cas: 3012-80-4) belongs to imidazole derivatives. The solubility of imidazoles in ethers is lower than that in alcohols and decreases with increasing chain length of the ethers . In contrast, the solubility of benzimidazoles in alcohols (C3–C6) is higher than in water and generally decreases with a Imidazole is incorporated into many important biological compounds. The most pervasive is the amino acid histidine, which has an imidazole side-chain. Histidine is present in many proteins and enzymes, e.g. by binding metal cofactors, as seen in hemoglobin.Synthetic Route of C9H8N2O
Referemce:
Imidazole – Wikipedia,
Imidazole | C3H4N2 – PubChem