Liang Jiang-Lin, Huang Jie-Sheng, Yu Xiao-Qi, Zhu Nianyong, Che Chi-Ming
Department of Chemistry and Open Laboratory of Chemical Biology of the Institute of Molecular Technology for Drug Discovery and Synthesis, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
Chemistry. 2002 Apr 2;8(7):1563-72. doi: 10.1002/1521-3765(20020402)8:7<1563::aid-chem1563>3.0.co;2-v.
Chiral metalloporphyrins [Mn(Por*)(OH)(MeOH)] (1) and [Ru(Por*)(CO)(EtOH)] (2) catalyze asymmetric aziridination of aromatic alkenes and asymmetric amidation of benzylic hydrocarbons to give moderate enantiomeric excesses. The mass balance in these nitrogen-atom-transfer processes has been examined. With PhI=NTs as the nitrogen source, the aziridination of styrenes, trans-stilbene, 2-vinylnaphthalene, indene, and 2,2-dimethylchromene catalyzed by complex 1 or 2 resulted in up to 99 % substrate conversions and up to 94 % aziridine selectivities, whereas the amidation of ethylbenzenes, indan, tetralin, 1-, and 2-ethylnaphthalene catalyzed by complex 2 led to substrate conversions of up to 32 % and amide selectivities of up to 91 %. Complex 1 or 2 can also catalyze the asymmetric amidation of 4-methoxyethylbenzene, tetralin, and 2-ethylnaphthalene with "PhI(OAc)(2) + NH(2)SO(2)Me", affording the N-substituted methanesulfonamides in up to 56 % ee with substrate conversions of up to 34 % and amide selectivities of up to 92 %. Extension of the "complex 1 + PhI=NTs" or "complex 1 + PhI(OAc)(2) + NH(2)R (R=Ts, Ns)" amidation protocol to a steroid resulted in diastereoselective amidation of cholesteryl acetate at the allylic C-H bonds at C-7 with substrate conversions of up to 49 % and amide selectivities of up to 90 % (alpha:beta ratio: up to 4.2:1). An aziridination- and amidation-active chiral bis(tosylimido)ruthenium(VI) porphyrin, [Ru(Por*)(NTs)(2)] (3), and a ruthenium porphyrin aziridine adduct, [Ru(Por*)(CO)(TsAz)] (4, TsAz=N-tosyl-2- (4-chlorophenyl)aziridine), have been isolated from the reaction of 2 with PhI=NTs and N-tosyl-2-(4-chlorophenyl)aziridine, respectively. The imidoruthenium porphyrin 3 could be an active species in the aziridination or amidation catalyzed by complex 2 described above. The second-order rate constants for the reactions of 3 with styrenes, 2-vinylnaphthalene, indene, ethylbenzenes, and 2-ethylnaphthalene range from 3.7-42.5x10(-3) dm(3) mol(-1) s(-1). An X-ray structure determination of complex 4 reveals an O- rather than N-coordination of the aziridine axial ligand. The fact that the N-tosylaziridine in 4 does not adopt an N-coordination mode disfavors a concerted pathway in the aziridination by a tosylimido ruthenium porphyrin active species.
手性金属卟啉[Mn(Por*)(OH)(MeOH)] (1)和[Ru(Por*)(CO)(EtOH)] (2)催化芳香烯烃的不对称氮杂环丙烷化反应以及苄基烃的不对称酰胺化反应，能给出中等的对映体过量值。已对这些氮原子转移过程中的质量平衡进行了研究。以PhI=NTs作为氮源，配合物1或2催化苯乙烯、反式二苯乙烯、2-乙烯基萘、茚和2,2-二甲基苯并吡喃的氮杂环丙烷化反应，底物转化率高达99%，氮杂环丙烷选择性高达94%，而配合物2催化乙苯、茚满、四氢萘、1-和2-乙基萘的酰胺化反应，底物转化率高达32%，酰胺选择性高达91%。配合物1或2也能催化4-甲氧基乙苯、四氢萘和2-乙基萘与“PhI(OAc)(2) + NH(2)SO(2)Me”的不对称酰胺化反应，得到对映体过量值高达56%的N-取代甲磺酰胺，底物转化率高达34%，酰胺选择性高达92%。将“配合物1 + PhI=NTs”或“配合物1 + PhI(OAc)(2) + NH(2)R (R = Ts, Ns)”酰胺化反应体系扩展至甾体，可实现胆固醇乙酸酯在C-7位烯丙基C-H键处的非对映选择性酰胺化反应，底物转化率高达49%，酰胺选择性高达90%（α:β比例高达4.2:1）。已分别从2与PhI=NTs以及N-对甲苯磺酰基-2-(4-氯苯基)氮杂环丙烷的反应中分离出手性双(对甲苯磺酰亚胺基)钌(VI)卟啉[Ru(Por*)(NTs)(2)] (3)和钌卟啉氮杂环丙烷加合物[Ru(Por*)(CO)(TsAz)] (4, TsAz = N-对甲苯磺酰基-2-(4-氯苯基)氮杂环丙烷)。亚胺基钌卟啉3可能是上述配合物2催化的氮杂环丙烷化或酰胺化反应中的活性物种。3与苯乙烯、2-乙烯基萘、茚、乙苯和2-乙基萘反应的二级速率常数范围为3.7 - 42.5×10(-3) dm(3) mol(-1) s(-1)。配合物4的X射线结构测定表明氮杂环丙烷轴向配体为O配位而非N配位。4中的N-对甲苯磺酰基氮杂环丙烷不采用N配位模式这一事实不利于对甲苯磺酰亚胺基钌卟啉活性物种进行氮杂环丙烷化反应的协同途径。
