Journal of the American Chemical Society p. 7606 - 7617 (1985)
Update date:2022-08-04
Topics: -Mechanism -Experimental terms -Chromium-Catalyzed Epoxidation -Oxochromium(V) Cations
Samsel, E. G.
Srinivasan, K.
Kochi, J. K.
The catalytic epoxidation of various olefins with iodosylbenzene is efficiently carried out by a series of chromium(III) cations CrIII(salen)+ (I) which are promoted by pyridine N-oxide (pyO) and related oxygen donors as the cocatalyst.Analysis of the catalytic rate profile and products establish the oxochromium(V) derivative O=Cr(salen)+ (II) and its donor adduct O=Cr(salen)(pyO)+ (III) as the reactive intermediates in the catalytic cycle.The successful isolation as well as the complete spectral analysis and structural characterization by X-ray crystallography of both II and III reveal the basis for oxygen activation in the O=CrV functionality.The mechanism of oxygen atom transfer involves the rate-limiting attack on the olefin by the electrophilic oxochromium(V) cation.The observation of benzaldehyde as a byproduct derived from the pyO-promoted C=C cleavage of styrene provides a method for unequivocally proving the existence of a transient intermediate during oxygen atom transfer.Thus the rate of olefin oxidation is found to be completely independent of the product-forming steps leading to epoxide and benzaldehyde, as they are modulated by added pyO.Steric effects, isotopic 18O tracers, stereochemistry, skeletal rearrangement, and substituent effects all provide mechanistic probes for the structure of the metastable intermediate.
View MoreQINGDAO DEVELOP chemistry Co.,Limited
Contact:+86-532-85807910
Address:98#Nanjing Road, Qingdao, China 266071
Contact:86 513 85512619
Address:Rm.1306, Building A, Wenfeng Mansion,168 Gongnong Road, Nantong Jiangsu China
A.M FOOD CHEMICAL CO., LIMITED
Contact:86-531-87100375
Address:20Floor,Bblock,1Building,pharma-valley,Jinan,China
Changzhou Litong Chemical Co., Ltd.
website:http://www.litonchem.com/
Contact:+86-519-86301238
Address:Laoba Rd, Hutang town Changzhou Jiangsu
Shanghai Hanhong Scientific Co.,Ltd.
website:http://www.chemvia.com
Contact:+86-21-64541543,54280654,13918533501
Address:Jiachuan Road 245
Doi:10.1021/je00043a036
(1986)Doi:10.1021/acs.jafc.0c07521
(2021)Doi:10.1039/jr9490002433
(1949)Doi:10.1002/hlca.19570400509
(1957)Doi:10.1016/j.bioorg.2021.104642
(2021)Doi:10.1021/ja00311a076
(1985)