乙酰丙酮和1-萘甲酸甲酯加成物C_(17)H_(18)O_4的晶体结构和分子力学计算

CRYSTAL STRUCTURE AND MOLECULAR MECHANICS CALCULATIONS OF THE ADDITION PRODUCT OF ACETYLACETONE AND METHYL 1-NAPHTHOATE, C_(17)H_(18)O_4

[2+2]环加成反应在有机合成中具有重要应用价值,其反应机理研究早已受到重视.现在β-二酮类的烯醇光环加成(即de Mayo反应)研究已从链烯扩展到芳核。乙酰丙酮和1-萘甲酸甲酯的光环加成的机理研究表明,这个反应不是一步完成的。光谱和~1H NMR数据基本确定中间体(1)的构型,但无法指定它的最终产物结构。X光单晶结构分析证明产物为具有张力的特殊碳架结构(2),而分子力学计算证明另一可能结构(3)具有更高的立体能。现在全面报导晶体结构和分子力学分析结果,从而揭示反应的全过程。

The structure of the product from the [2 + 2] photocycloaddition of acetylacetone to methyl 1-naphthoate was determined by X-ray crystallography. Crystal data. C_(17)H_(18)O_4, triclinic, P_1^-, a = 7.401(1), b = 7.656(1), c = 13.882(1) A , a = 84.75(1), β = 86.49(1), γ = 65.08(1)°, V = 710.2A^3, Z = 2, D_c = 1.339g.cm^(-3), μ(MoK_a) = 1.0cm^(-1), F(000)=304. The structure was solved by direct methods and refined to final R= 0.049 for 2442 MoKa reflections. The particular bridged structure of the product molecule indicates a [2 + 2 + 2] intramolecular cycloaddition in succession to the primary [2+2] photocycloaddition. Molecular mechanics calculations confirmed further that the molecular structure of the ultimate product takes a configuration of comparatively favourable steric energy even though the bridged structure itself is rather strained.