Enantioselective[4+2]-Cycloaddition Reaction of a Photochemically Generatedo-Quinodimethane: Mechanistic Details, Association Studies, and Pressure Effects
作者:Benjamin Grosch、Caroline N. Orlebar、Eberhardt Herdtweck、Masayuki Kaneda、Takehiko Wada、Yoshihisa Inoue、Thorsten Bach
DOI:10.1002/chem.200306049
日期:2004.5.3
the photocycloaddition as a result of the lower product association to 1. The intermediate (E)-dienol 8 was spectroscopically detected at -196 degrees C in an EPA (diethyl ether/isopentane/ethanol) glass matrix. The association of the substrate 2 to the complexing agent 1 was studied by circular dichroism (CD) titration. The measured association constant (K(A)) was 589 M(-1) at room temperature (25 degrees
由间氨基苯甲酸和3-乙氧基丙烯酰氯(4)制备1,2,3,4-四氢-2-氧喹啉-5-醛(2),总产率为19%。在甲苯溶液中照射后,化合物2与各种双亲物进行光化学诱导的[4 + 2]-环加成反应。用丙烯腈(9a)作为亲二烯体获得外向产物10a,而丙烯酸甲酯(9b)和富马酸二甲酯(9c)提供了内产物11b和11c(69-77%收率)。反应在-60℃下在手性络合剂1(1.2当量)的存在下以优异的对映选择性(91-94%ee)进行。对映体过量在光环加成过程中由于产物缔合度降低到1。在-196℃下在EPA(二乙醚/异戊烷/乙醇)玻璃基质中以光谱法检测到中间体(E)-二烯醇8。通过圆二色性(CD)滴定研究了底物2与络合剂1的缔合。在室温(25摄氏度)和常压(0.1 MPa)下测得的缔合常数(K(A))为589 M(-1)。压力增加导致联想增加。在400 MPa下,K(A)的测量值为703 M(-1)。尽