An unprecedented enantioselective synthesis of 3-substituted benzoxaboroles has been developed. An in situ generated ortho-boronic acid containing chalcone provides the chiral benzoxaboroles via an asymmetric oxa-Michael addition of hydroxyl group attached to the boronic acid triggered by the cinchona alkaloid based chiral amino-squaramide catalysts. In general, good yields with good to excellent
Phosphine-Mediated Sequential [2+4]/[2+3] Annulation to Construct Pyrroloquinolines
作者:Junhui Lin、Yannan Zhu、Wei Cai、You Huang
DOI:10.1021/acs.orglett.1c04388
日期:2022.3.4
A domino [2+4]/[2+3] sequentialannulation reaction of MBH carbonates with N-unprotected indoles has been developed to provide various pyrroloquinoline derivatives in ≤94% yield and 20:1 dr. The reaction could be either mediated by stoichiometric PCy3 or catalyzed by R3PO via PIII/PV═O redox cycling in the presence of phenylsilane. This method assembles polycyclic 1,7-fused indoles in one step diastereoselectively
MBH 碳酸盐与 N-未保护的吲哚的多米诺 [2+4]/[2+3] 顺序环化反应已被开发,以提供≤94% 产率和 20:1 dr 的各种吡咯并喹啉衍生物。该反应可以由化学计量的 PCy 3介导,也可以由 R 3 PO 在苯基硅烷存在下通过 P III /P V = O 氧化还原循环催化。该方法一步非对映选择性地组装多环 1,7-稠合吲哚。
Enantioselective Synthesis of Cyclohexadienone Containing Spiroketals via DyKat Ketalization/oxa-Michael Addition Cascade
An oxidative dearomatization of phenol followed by a dynamic kinetic (DyKat) ketalization/oxa-Michael addition cascade using cinchona alkaloid-based chiral bifunctional amino-squaramide catalysts is reported. A broad array of sterically hindered [5,5]-spiroketals attached to a cyclohexadienone moiety in spiro-fashion is synthesized in an enantiopure form. Further, the methodology was optimized and
Organocatalytic, Enantioselective Synthesis of Cyclohexadienone Containing Hindered Spirocyclic Ethers through an Oxidative Dearomatization/Oxa-Michael Addition Sequence
unprecedented enantioselective oxa‐Michael reaction of α‐tertiary alcohols using cinchona‐alkaloid‐based chiral bifunctional squaramide catalysts is reported. An oxidative dearomatization of phenol followed by an enantioselective oxa‐Michael addition sequence provided a broad array of chiral sterically hindered tetrahydrofurans and tetrahydropyrans attached to a cyclohexadienone moiety in spiro fashion.
Enantio- and Diastereoselective Organocatalytic Conjugate Additions of Nitroalkanes to Enone Diesters
作者:Matthew A. Horwitz、Jennifer L. Fulton、Jeffrey S. Johnson
DOI:10.1021/acs.orglett.7b02735
日期:2017.11.3
catalyzed the addition reaction with consistently excellent stereoselectivities and yields across a wide range of substrates. By the use of the gem-diester functional handle present in the adducts, local desymmetrization via diastereotopic group discrimination was demonstrated, and a polyfunctionalized lactam with threecontiguousstereocenters was synthesized.