Enantioselective ring-contraction reactions have not been widely reported. We have developed an enantioselective ring contraction of 5,6-dihydro-2H-benzo[b][1,4]oxazocines, affording enantiomerically enriched 3,4-dihydro-2H-1,4-benzoxazine derivatives as single regioisomers. An acidic additive is necessary in order to obtain the products with good yields and enantiomeric ratios (up to 93% yield, 98:2
对映选择性环收缩反应尚未被广泛报道。我们开发了 5,6-dihydro-2 H -benzo [ b ][1,4]oxazocines 的对映选择性环收缩,提供对映体富集的 3,4-dihydro-2 H -1,4-benzoxazine衍生物作为单一区域异构体。为了获得具有良好产率和对映体比率(高达 93% 产率,98:2 er)的产品,酸性添加剂是必需的。该反应成功地进行了克级反应,产物易于衍生化。
Palladium-catalyzed oxamidation of alkenes: A new approach to benzoxazolidines
作者:Niranjan Panda、Sushree Arpitabala Yadav
DOI:10.1016/j.tet.2018.02.012
日期:2018.3
A novel palladium catalyzed protocol for the synthesis of benzoxazolidine by the reaction sulfamidophenol and terminal alkene was developed. This oxamidation process is simple and does not require any ligand, base or inert atmosphere for the overall transformation. From control experiments, it is apparent that the cross-coupling reaction proceeds with initial formation of enesulfonamide which undergoes
Palladium-Catalyzed Asymmetric Aminohydroxylation of 1,3-Dienes
作者:Hong-Cheng Shen、Yu-Feng Wu、Ying Zhang、Lian-Feng Fan、Zhi-Yong Han、Liu-Zhu Gong
DOI:10.1002/anie.201712350
日期:2018.2.23
A PdII‐catalyzed asymmetricaminohydroxylation of 1,3‐dienes with N‐tosyl‐2‐aminophenols was developed by making use of a chiral pyridinebis(oxazoline) ligand. The highly regioselective reaction provides direct and efficient access to chiral 3,4‐dihydro‐2H‐1,4‐benzoxazines in high yield and enantioselectivity (up to 96:4 e.r.). The reaction employs readily available N‐tosyl‐2‐aminophenols as a unique
利用手性吡啶双(恶唑啉)配体开发了Pd II催化的1,3-二烯与N-甲苯磺酰基-2-氨基苯酚的不对称氨基羟基化反应。高度区域选择性反应可直接高效地获得手性3,4-二氢-2 H -1,4-苯并恶嗪,且产率高且对映选择性高(高达96:4 er)。该反应采用现成的N-甲苯磺酰基-2-氨基苯酚作为独特的氨基羟基化试剂,是已知不对称氨基羟基化方法的补充。
Acid-Catalysed Hydrolysis of Some Aromatic Cyclic Sulfamates
作者:Yunus Bekdemir、Halil Kutuk、Sibel Celik、John G. Tillett
DOI:10.1080/10426500210670
日期:2002.4.1
The acid catalysed hydrolysis of some cyclic sulfamates, X-3-(p-tolylsulfonyl)-1,2,3-benzoxathiazole 2,2-dioxides ( 1a , X = Me; 1b , X = H; 1c , X = Cl; 1d , X = NO 2 ) have been studied in concentrated aqueous sulfuric and perchloric acid solutions. Analysis of the data by the Excess Acidity Method, activation parameters, substituent, solvent deuterium isotope effect and order of the catalytic effects
一些环状氨基磺酸盐的酸催化水解,X-3-(p-tolylsulfonyl)-1,2,3-benzoxathiazole 2,2-dioxides (1a, X = Me; 1b, X = H; 1c, X = Cl; 1d , X = NO 2 ) 在浓硫酸和高氯酸水溶液中进行了研究。过量酸度法的数据分析、活化参数、取代基、溶剂氘同位素效应和酸的催化效应顺序都与研究范围内的A-1机理一致。
Synthesis of Benzoxazoles via an Amine-Catalyzed [4 + 1] Annulation
作者:Aiguo Song、Xiaobei Chen、Xixi Song、Xinshuai Zhang、Shilei Zhang、Wei Wang
DOI:10.1021/ol400988e
日期:2013.5.17
An unprecedented simple pyrrolidine catalyzed [4 + 1] annulation reaction of ynals with N-protected-2-aminophenols Is reported. The utilization of the unique property and reactivity of the C C triple bond in ynals leads to two consecutive conjugate addition reactions at the same beta-position with pyrrolidine via iminium activation. The powerful cascade process affords a new alternative approach to biologically and synthetically important benzoxazoles in high yields (83-95%).