Phosphine-Initiated General Base Catalysis: Facile Access to Benzannulated 1,3-Diheteroatom Five-Membered Rings via Double-Michael Reactions of Allenes
作者:Judy Szeto、Vardhineedi Sriramurthy、Ohyun Kwon
DOI:10.1021/ol201730q
日期:2011.10.21
General base-catalyzed double-Michael reactions of allenes with various dinucleophiles are described. The reactions are facilitated most efficiently by a catalytic amount of trimethylphosphine, affording six types of C2-functionalized benzannulated five-membered heterocycles: benzimidazolines, benzoxazolines, benzothiazolines, 1,3-benzodioxoles, 1,3-benzoxathioles, and 1,3-benzodithioles. This atom-economical
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 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。