Catalytic Asymmetric Hydrogenation of N-Boc-Imidazoles and Oxazoles
摘要:
Substituted imidazoles and oxazoles were respectively hydrogenated into the corresponding chiral imidazolines and oxazolines (up to 99% ee). The highly enantioselective hydrogenation was achieved by using the chiral ruthenium catalyst, which is generated from Ru(eta(3)-methallyl)(2)(cod) and a trans-chelating chiral bisphosphine ligand, PhTRAP. This is the first successful catalytic asymmetric reduction of 5-membered aromatic rings containing two or more heteroatoms.
Photochemical Transformation of <i>O</i>
-(β-Arylethyl) Arylimidates into 2,4-Diaryl-5-iodoxazoles with 1,3-Diiodo-5,5-dimethylhydantoin
作者:Aya Saito、Hideo Togo
DOI:10.1002/ejoc.202000383
日期:2020.6.16
2,4‐Diaryl‐5‐iodoxazoles could be obtained by the treatment of O ‐(β‐arylethyl) arylimidates with 1,3‐diiodo‐5,5‐dimethylhydantoin (DIH) under irradiation with a tungsten lamp. This reaction proceeds through multiple stets, i.e., formation of N ‐iodoimidate, iminyl radical, 1,5‐H shift, 5‐exo‐tet cyclization to oxazoline, oxidation to oxazole, and iodination to 5‐iodoxazole.
A new and efficient method for the synthesis of 4-aryl-2-phenyloxazoles is described which is based upon the reaction of α-[(2,4-dinitrobenzene)sulfonyl]oxy ketone intermediates with benzamide in ionicliquid.
Radical cascade synthesis of azoles <i>via</i> tandem hydrogen atom transfer
作者:Andrew D. Chen、James H. Herbort、Ethan A. Wappes、Kohki M. Nakafuku、Darsheed N. Mustafa、David A. Nagib
DOI:10.1039/c9sc06239d
日期:——
A radical cascade enables rapid, modular access to five-membered heteroarenes, including oxazoles and imidazoles, through a regio- and chemo-selective β C–H bis-functionalization.