Lewis-acid catalysis of photochemical reactions. 9. Structure and photoisomerization of (E)- and (Z)-cinnamamides and their Lewis acid complexes
摘要:
The spectroscopic properties and photoisomerization reactions of several (E)- and (Z)-cinnamamides have been investigated in the absence and presence of the strong Lewis acid BF3. The (E)-cinnamamides are essentially planar and exist predominantly in the enone s-cis conformation, except in the case of the alpha-methyl tertiary amide which adopts the s-trans conformation in order to minimize nonbonded repulsion. The (Z)-cinnamamides exist predominantly in the highly nonplanar s-trans conformation. This unusual conformational preference is attributed to intramolecular charge transfer from the aromatic to amide functionality. Photoisomerization efficiencies are dependent upon N-alkylation, aromatic substitution, alpha-alkylation, solvent, and excitation wavelength. These effects are attributed to the existence of two lowest energy pi,pi* singlet states (one reactive and one nonreactive) whose relative energies are dependent upon substitution. The cinnamamides from 1:1 complexes with BF3 with equilibrium constants > 10(3). Complexation alters both the electronic structure and photochemical behavior of the cinnamamides. Quantitative E --> Z isomerization has been observed for the BF3 complexes of two tertiary amides.
Catalytic, Transition-Metal-Free Semireduction of Propiolamide Derivatives: Scope and Mechanistic Investigation
作者:R. Justin Grams、Christopher J. Garcia、Connor Szwetkowski、Webster L. Santos
DOI:10.1021/acs.orglett.0c02567
日期:2020.9.4
We report a transition-metal-free trans-selective semireduction of alkynes with pinacolborane and catalytic potassium tert-butoxide. A variety of 3-substituted primary and secondary propiolamides, including an analog of FK866, a potent nicotinamide mononucleotide adenyltransferase (NMNAT) inhibitor, are reduced to the corresponding (E)-3-substituted acrylamide derivatives in up to 99% yield with >99:1
我们报道了频哪醇硼烷和催化叔丁醇钾对炔烃的无过渡金属反式选择性半还原。各种 3-取代的一级和二级丙炔酰胺,包括 FK866 的类似物(一种有效的烟酰胺单核苷酸腺苷酸转移酶 (NMNAT) 抑制剂),可被还原为相应的 ( E )-3-取代的丙烯酰胺衍生物,产率高达 99%,且 >99 :1 E / Z选择性。机理研究表明,活化的路易斯酸碱配合物将氢化物转移到α-碳上,然后以反式方式快速质子化。
Organocatalytic
<i>Trans</i>
Semireduction of Primary and Secondary Propiolamides: Substrate Scope and Mechanistic Studies
作者:R. Justin Grams、Monsurat M. Lawal、Connor Szwetkowski、Daniel Foster、Carol Ann Rosenblum、Carla Slebodnick、Valerie Vaissier Welborn、Webster L. Santos
DOI:10.1002/adsc.202101020
日期:2022.1.4
We report a chemoselective, phosphine-catalyzed semireduction of primary and secondary propiolamides. In the presence of stoichiometric pinacolborane and catalytic n-tributylphosphine, a variety of propiolamides were successfully converted to the corresponding acrylamides in excellent yield with (E)-stereoselectivity. The reaction condition is tolerant of various functional groups including alkene
我们报告了初级和次级丙酰胺的化学选择性、膦催化的半还原反应。在化学计量的频哪醇硼烷和催化正三丁基膦的存在下,各种丙酰胺以优异的收率成功转化为相应的丙烯酰胺,具有(E)-立体选择性。反应条件可以容忍各种官能团,包括烯烃、炔烃、酮或酯。氘标记研究表明,来自活化频哪醇硼烷的氢化物被添加到 α-碳,酰胺氮上的质子被 β-碳提取以提供 ( E )-丙烯酰胺。DFT 计算揭示了 ( E )- 在 ( Z)-异构体。
Mild Zinc-Promoted Horner-Wadsworth-Emmons Reactions of Diprotic Phosphonate Reagents
作者:Paul Helquist、Douglas Schauer
DOI:10.1055/s-2006-950292
日期:2006.11
We report the development of a mild protocol for the Horner-Wadsworth-Emmons reaction of diprotic phosphonates that makes use of a zinc triflate promoter in the presence of mild tertiary amine bases to produce α,β-unsaturated carboxylic acids and amides.
Manganese Catalyzed Enantioselective Epoxidation of
<i>α</i>
,
<i>β</i>
‐Unsaturated Amides with H
<sub>2</sub>
O
<sub>2</sub>
作者:Roman V. Ottenbacher、Vladimir I. Kurganskiy、Evgenii P. Talsi、Konstantin P. Bryliakov
DOI:10.1002/adsc.202100198
日期:2021.6.8
Herewith, we report the enantioselectiveepoxidation of electron-deficient cis- and trans-α,β-unsaturated amides with the environmentally benign oxidant H2O2. The catalysts - manganese complexes with bis-amino-bis-pyridine and structurally related ligands - exhibit reasonably high efficiency (up to 100 TON) and excellent chemo- and enantioselectivity (up to 100% and 99% ee, respectively). Crucially
在此,我们报告了缺电子顺式和反式-α,β-不饱和酰胺与环境友好型氧化剂H 2 O 2的对映选择性环氧化反应。催化剂——锰与双氨基双吡啶和结构相关配体的配合物——表现出相当高的效率(高达 100 吨)和优异的化学和对映选择性(分别高达 100% 和 99% ee)。至关重要的是,顺式-enamides环氧化的对映选择性和产率用NH部分的存在,其效果可以通过之间的氢键相互作用来解释被显着增强的顺-烯酰胺底物和锰基氧转移物质。
Glover,S.A.; Goosen,A., Journal of the Chemical Society. Perkin transactions I, 1977, p. 1348 - 1356