First I2–K2CO3-promoted sequential C–N and C–O bond forming approach for one-pot synthesis of 1,4-benzoxazines
作者:Sunil K. Singh、Anil K. Bajpai、Rajesh Saini
DOI:10.1016/j.tetlet.2013.10.092
日期:2013.12
system for the one-potsynthesis of 3-aryl-2H-benz[1,4]oxazine viarapid CN and C–O bond formation. No by-product formation, operational simplicity, ambient temperature, and high yield (85–94%) are the attractive features of the envisaged reaction. The reported one-potsynthesis of 1,4-benzoxazine involves the application of I2–K2CO3 catalyst system for the first time and proceeds via in situ imine
已经发现,I 2 –K 2 CO 3组合是一种通过快速CN和C–O一锅合成3-芳基-2 H-苯并[1,4]恶嗪的有效,可重复使用和廉价的催化剂体系。键的形成。没有副产物的形成,操作简便,环境温度和高产率(85-94%)是预期反应的吸引人的特征。已报道的1,4-苯并恶嗪的一锅法合成首次涉及I 2 -K 2 CO 3催化剂体系的应用,并通过原位亚胺形成,随后进行分子内环转化级联反应进行。
Lewis Base Organocatalyzed Enantioselective Hydrosilylation of 1,4-Benzoxazines
A chiral Lewisbaseorganocatalyzedenantioselectivehydrosilylation of 1,4-benzoxazines is presented. The reactions afforded various enantioenriched 3-substituted dihydro-2 H -1,4-benzoxazines with high yields (up to 98%) in moderate enantioselectivities (up to 87% ee).
提出了一种手性路易斯碱有机催化的 1,4-苯并恶嗪的对映选择性氢化硅烷化。该反应以中等对映选择性(高达 87% ee)的高产率(高达 98%)提供了各种对映体富集的 3-取代二氢-2 H -1,4-苯并恶嗪。
An Organocatalyst Bearing Stereogenic Carbon and Sulfur Centers as an Efficient Promoter for Enantioselective Hydrosilylation of 1,4-Benzooxazines
作者:Xiang-Wei Liu、Chao Wang、Yan Yan、Yong-Qiang Wang、Jian Sun
DOI:10.1021/jo400187e
日期:2013.6.21
The efficient and enantioselective hydrosilylation of 3-aryl-1,4-benzooxazines was achieved using an l-phenyl alanine derived new Lewis base catalyst bearing stereogenic carbon and sulfur centers. In the presence of 2 mol % of catalyst, a broad range of 3-aryl-1,4-benzooxazines were hydrosilylated to afford the corresponding chiral 3-aryl-3,4-dihydro-2H-1,4-benzooxazine products with good to high yields (66-98%) and enantioselectivities (70-99% ee). This method provides an alternative approach with great practical application potential to access chiral 3-aryl-3,4-dihydro-2H-1,4-benzooxazines.
Kinetic Resolution by Lithiation: Highly Enantioselective Synthesis of Substituted Dihydrobenzoxazines and Tetrahydroquinoxalines
作者:Iain Coldham、Ashraf El-Tunsi、Nicholas Carter、Song-Hee Yeo、Joshua D. Priest、Anthony Choi、Carolin M. Kobras、Soneni Ndlovu、Ilaria Proietti Silvestri、Andrew K. Fenton
DOI:10.1055/a-1638-2478
日期:2022.1
4-benzoxazines using n-butyllithium and the chiral ligand sparteine. The enantioenrichment remained high on removing the tert-butoxycarbonyl (Boc) protectinggroup. The intermediate organolithium undergoes ring opening to an enamine. The kinetic resolution was extended to give enantiomerically enriched substituted 1,2,3,4-tetrahydroquinoxalines and was applied to the synthesis of an analogue of the antibiotic