Asymmetric Synthesis of Propargylamides via 3,3‘-Disubstituted Binaphthol-Modified Alkynylboronates
摘要:
Alkynylboronates derived from 3,3'-disubstituted-2,2'-binaphthols react with various N-acylimines to give the expected chiral propargylamides with up to 99% ee. This new methodology was applied to the first enantioselective synthesis of the antitubulin agent (-)-N-acetylcolchinol.
Asymmetric Synthesis of Propargylamides via 3,3‘-Disubstituted Binaphthol-Modified Alkynylboronates
摘要:
Alkynylboronates derived from 3,3'-disubstituted-2,2'-binaphthols react with various N-acylimines to give the expected chiral propargylamides with up to 99% ee. This new methodology was applied to the first enantioselective synthesis of the antitubulin agent (-)-N-acetylcolchinol.
Silyl Imine Electrophiles in Enantioselective Catalysis: A Rosetta Stone for Peptide Homologation, Enabling Diverse <i>N</i>-Protected Aryl Glycines from Aldehydes in Three Steps
作者:Dawn M. Makley、Jeffrey N. Johnston
DOI:10.1021/ol501297a
日期:2014.6.6
es serve in the Bis(AMidine)-catalyzed addition of bromonitromethane with a high degree of enantioselection. This allows for the production of a range of protected α-bromo nitroalkane donors (including Fmoc) for use in Umpolung Amide Synthesis (UmAS). Hence, peptide homologation with nonnatural aryl glycine amino acids is achieved in three steps from aromaticaldehydes, which are plentiful and inexpensive
the precursor for the reductivecomplexation of the imines N-(4-methylbenzylidene)aniline (2e) and 2-methyl-1-pyrroline (7), the formation of diazatitanacyclopentanes by McMurry-like C–C coupling is found. A six-membered titanacycle 8 is obtained by a Michael-like coupling reaction of 7. By these insights, it is possible to derive a general reaction pattern for low-valent titanium centers with imines
Chiral Phosphoric Acid Catalyzed Enantioselective [4 + 2] Cycloaddition Reaction of α-Fluorostyrenes with Imines
作者:Jun Kikuchi、Haiting Ye、Masahiro Terada
DOI:10.1021/acs.orglett.0c03360
日期:2020.11.20
An enantioselective [4 + 2] cycloadditionreaction of α-fluorostyrenes with N-benzoyl imines was demonstrated using a chiral phosphoric acid catalyst. Cycloaddition products having fluorine functionality were formed in high yields with excellent diastereo- and enantioselectivities. Further manipulation of the enantioenriched cycloaddition product with silyl enol ether in the presence of BiCl3 catalyst
使用手性磷酸催化剂证明了α-氟苯乙烯与N-苯甲酰基亚胺的对映选择性[4 + 2]环加成反应。具有氟官能团的环加成产物以高收率形成,具有优异的非对映选择性和对映选择性。在BiCl 3催化剂存在下,用甲硅烷基烯醇醚进一步处理对映体富集的环加成产物,得到的取代产物可通过选择性碳-氟键裂解保留二氢-4 H -1,3-恶嗪骨架,而不会损失对映体过量。
Imines in the Titanium Coordination Sphere: η
<sup>1</sup>
‐Imine Complexes as Sources of Azavinylidenes and Four‐Membered Imine–Amido‐
<i>N</i>
,
<i>N′</i>
Chelates
In titanium imine complexes the ligand can exhibit several bonding modes. While η2-imine complexes are intermediates in several catalytic transformations and well investigated, the potential of imines to coordinate through the lone pair of electrons of the nitrogen atom by a dative bond to the titanium center is studied herein. The formation of several bis-η1 complexes by the reaction of Schiff bases
Convenient Access to Primary Amines by Employing the Barbier-Type Reaction of <i>N</i>-(Trimethylsilyl)imines Derived from Aromatic and Aliphatic Aldehydes
作者:Ferenc Gyenes、Kathryn E. Bergmann、John T. Welch
DOI:10.1021/jo971061r
日期:1998.5.1
A new versatile preparation of primary amines via benzylation of aromatic and aliphatic aldimines is described. Sonochemical and traditional methods for generation of the reactive intermediates are compared and contrasted. Competitive reactions were analyzed via free energy relationships to support the proposed alkylative mechanism.