66406-90-4Relevant academic research and scientific papers
Controllable, Sequential, and Stereoselective C-H Allylic Alkylation of Alkenes
Qin, Ling,Sharique, Mohammed,Tambar, Uttam K.
supporting information, p. 17305 - 17313 (2019/11/03)
The direct conversion of C-H bonds into new C-C bonds represents a powerful approach to generate complex molecules from simple starting materials. However, a general and controllable method for the sequential conversion of a methyl group into a fully substituted carbon center remains a challenge. We report a new method for the selective and sequential replacement of three C-H bonds at the allylic position of propylene and other simple terminal alkenes with different carbon groups derived from Grignard reagents. A copper catalyst and electron-rich biaryl phosphine ligand facilitate the formation of allylic alkylation products in high branch selectivity. We also present conditions for the generation of enantioenriched allylic alkylation products in the presence of catalytic copper and a chiral phosphine ligand. With this approach, diverse and complex products with substituted carbon centers can be generated from simple and abundant feedstock chemicals.
Thiyl radical promoted chemo- and regioselective oxidation of CC bonds using molecular oxygen: Via iron catalysis
Xiong, Baojian,Zeng, Xiaoqin,Geng, Shasha,Chen, Shuo,He, Yun,Feng, Zhang
, p. 4521 - 4527 (2018/10/17)
The first example of the thiyl radical promoted ligand-free iron-catalyzed oxidative cleavage of alkenes using molecular oxygen (1 atm) has been developed. The reaction proceeds under mild reaction conditions with high efficiency and high chemo- and regioselectivity. It features a broad substrate scope and excellent functional group compatibility, enabling facile access to valuable molecules for application in medicinal chemistry. Preliminary mechanistic studies reveal that a vital intermediate dioxetane might be involved in the reaction and a thiyl radical plays a synergistic role in facilitating the selective oxidation of the CC bond.
Intramolecular Nucleophilic Addition to Unsaturated Carbon. Dependence of Cyclization Efficiency on the Method of Carbon-Carbon Bond Cleavage Utilized To Generate the Reactive Species
Paquette, Leo A.,Gilday, John P.,Maynard, George D.
, p. 5044 - 5053 (2007/10/02)
The following three reactions have been studied for the purpose of comparing their intrinsic ability to generate carbanionic intermediates capable of intramolecular cyclization: (a) the Haller-Bauer cleavage of ketones 15a and 15b, as well as the (S)-(+)-antipode of 15a (viz. 47); (b) the base-promoted cleavage of 1,1-diarylcarbinols 16a and 16b; (c) decarboxylative elimination within the methyllithium adducts of carboxylic acids 17a and 17b.The Haller-Bauer process proceeds predominantly via carbanion intermediates, which most often experience protonation to give 18 an d 21.Cyclization becomes possible, however, under certain circumstances and reaches a maximum of 33percent with NaNH2 in benzene.Using (+)-47 as a probe, it has been possible to ascertain that 56percent of the reactive intermediate molecules racemize and that only the racemic species generates cyclic product.On the other hand, the Cram-type cleavages of 16a and 16b proceed mainly by homolytic cleavage to generate the benzophenone radical anion and free-radical intermediate.The latter dimerize, capture solvent, and abstract hydrogen to varying degrees depending upon counterion and solvent.Finally, reactions of type c are the most efficient at effecting intramolecular ring closure.
