An Organocatalyst Bearing Stereogenic Carbon and Sulfur Centers as an Efficient Promoter for Enantioselective Hydrosilylation of 1,4-Benzooxazines
摘要:
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.
A highlyefficient synthesis of novel spirocyclic benzoxazine‐indenes from benzoxazine and alkynes via iminedirected C–H activation/annulation using rhodium catalyst was reported. The methodology could be applied to various benzoxazines and alkynes, giving the corresponding spiro indenyl benzoxazine as spirocycle products in good yields.
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。
Asymmetric Pnictogen-Bonding Catalysis: Transfer Hydrogenation by a Chiral Antimony(V) Cation/Anion Pair
作者:Jian Zhang、Jun Wei、Wei-Yi Ding、Shaoyu Li、Shao-Hua Xiang、Bin Tan
DOI:10.1021/jacs.1c02808
日期:2021.5.5
Pnictogen-bonding catalysisbased on σ-hole interactions has recently attracted the attention of synthetic chemists. As a proof-of-concept for asymmetric pnictogen-bonding catalysis, we report herein an enantioselective transfer hydrogenation of benzoxazines catalyzed by a novel chiral antimony cation/anion pair. The chiral pnictogen catalyst library could be rapidly accessed from triarylstibine with
The highly enantioselective hydrogenation of 3-aryl-2H-1,4-benzoxazines was achieved using the (cyclooctadiene)iridium chloride dimer/(S)-SegPhos/iodine [Ir(COD)Cl]2/(S)-SegPhos/I2} system as catalyst with up to 92% ee. The 3-styryl-2H-1,4-benzoxazine derivatives were also hydrogenated by the iridium catalyst and Pd/C in two consecutive steps whereby 93–95% ee values were obtained.
使用(环辛二烯)铱氯化二聚物/(S)-SegPhos /碘[Ir(COD)Cl] 2 /(S)-SegPhos实现对3-芳基2 H -1,4-苯并恶嗪的高度对映选择性氢化/ I 2 }体系作为催化剂,ee最高可达92%。3-styryl-2 H -1,4-苯并恶嗪衍生物还通过铱催化剂和Pd / C在两个连续的步骤中进行氢化,从而获得93-95%ee值。
Synthesis of spiropyrans <i>via</i> the Rh(<scp>iii</scp>)-catalyzed annulation of 3-aryl-2<i>H</i>-benzo[<i>b</i>][1,4]oxazines with diazo ketoesters
Rh(III)-catalyzed 1:2 coupling of 3-aryl-2H-benzo[b][1,4]oxazines with α-diazo-β-ketoesters has been realized for mild synthesis of spiropyrans. The reaction proceeded via twofold C-H activation followed by unusual [3+3] and [4+2] annulation with decent functional group tolerance. Moreover, A pyranoid-skelecton intermediate has been isolated as a key intermediate as a result of mono-alkylation and