Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Org Biomol Chem. 2011 Apr 21;9(8):2868-77. doi: 10.1039/c0ob01143f. Epub 2011 Mar 9.
The treatment of β,γ-unsaturated α-ketoesters with phenols in the presence of trityl chloride and 4 Å molecular sieves in refluxing trifluoroacetic acid afforded 4-aryl-2H-chromenes in high yields, in which a reverse of the regiochemistry of Jørgensen-Rutjes chromane synthesis was observed. The isolation of 4H-chromene intermediates, confirmed by single-crystal X-ray analysis, indicates that the early stage of the reaction involves a Friedel-Crafts alkylation/cyclodehydration processes. Stirring of the 4H-chromene intermediate with trityl chloride in deuterotrifluoroacetic acid under reflux afforded the 2H-chromene and triphenylmethane in high yields, which implies the late stage of the reaction involves a hydrogen transfer process. Highly selective derivation of the hydroxyl esters to the corresponding hydroxyl amides, amino acids, amino esters and Friedel-Crafts adducts was further accomplished. Our endeavors will lead to a better understanding of the controlling elements behind their structural motifs. The products were confirmed unambiguously from their spectra and by single-crystal X-ray analysis.
在三苯甲基氯和 4 Å 分子筛存在下，β,γ-不饱和α-酮酯与酚在回流三氟乙酸中反应，以高产率得到 4-芳基-2H-色烯，其中观察到 Jørgensen-Rutjes 色烷合成的区域化学的反转。通过单晶 X 射线分析确认的 4H-色烯中间体的分离表明，反应的早期阶段涉及 Friedel-Crafts 烷基化/环脱水过程。在回流的氘代三氟乙酸中，将 4H-色烯中间体与三苯甲基氯搅拌，以高产率得到 2H-色烯和三苯甲烷，这意味着反应的后期阶段涉及氢转移过程。羟基酯的高度选择性衍生为相应的羟基酰胺、氨基酸、氨基酯和 Friedel-Crafts 加合物也进一步完成。我们的努力将有助于更好地理解它们结构基序背后的控制因素。产物通过其光谱和单晶 X 射线分析得到明确确认。
