Syntheses of extreme sterically hindered 4-methoxyboronic acids
摘要:
4-Iodoanisoles 3a,b, 3d and 4-bromoanisoles 4a-d were readily obtained. An extreme steric hindrance precluded obtaining 3c. Catalytic borylation of 3a,b, 3d followed by hydrolysis of boronic ester 26a,b, 26d easily provided the boronic acids 5a,b, 5d. Compounds Sa and 5d were also synthesised, starting from 4a and 4d, by halogen/metal exchange. Because of a too important steric hindrance, this last reaction failed with 4c and 4b led to the unexpected but stable boronic ester 6. The final obtaining of 5b required a strongly basic hydrolysis with heating. (C) 2009 Elsevier Ltd. All rights reserved.
Syntheses of extreme sterically hindered 4-methoxyboronic acids
摘要:
4-Iodoanisoles 3a,b, 3d and 4-bromoanisoles 4a-d were readily obtained. An extreme steric hindrance precluded obtaining 3c. Catalytic borylation of 3a,b, 3d followed by hydrolysis of boronic ester 26a,b, 26d easily provided the boronic acids 5a,b, 5d. Compounds Sa and 5d were also synthesised, starting from 4a and 4d, by halogen/metal exchange. Because of a too important steric hindrance, this last reaction failed with 4c and 4b led to the unexpected but stable boronic ester 6. The final obtaining of 5b required a strongly basic hydrolysis with heating. (C) 2009 Elsevier Ltd. All rights reserved.
Enantioselective Ruthenium-Catalyzed Benzocyclobutenone–Ketol Cycloaddition: Merging C–C Bond Activation and Transfer Hydrogenative Coupling for Type II Polyketide Construction
作者:Brett R. Ambler、Ben W. H. Turnbull、Sankar Rao Suravarapu、Maulen M. Uteuliyev、Nancy O. Huynh、Michael J. Krische
DOI:10.1021/jacs.8b05724
日期:2018.7.25
The first enantioselective intermolecular metal-catalyzed cycloadditions of benzocyclobutenones via C-C bond oxidative addition are described. In the presence of a ruthenium(0) complex modified by ( R)-DM-SEGPHOS, tetralone-derived ketols and benzocyclobutenones combine to form cycloadducts with complete regio- and diastereoselectivity and high enantioselectivity. Using this method, the "bay region"
描述了苯并环丁烯酮通过 CC 键氧化加成的第一个对映选择性分子间金属催化环加成。在 (R)-DM-SEGPHOS 修饰的钌 (0) 络合物存在下,四氢萘酮衍生的酮醇和苯并环丁烯酮结合形成具有完全区域和非对映选择性以及高对映选择性的环加合物。利用该方法制备了安古环素天然产物沙霉素的“湾区”亚结构。