Stereodefined Access to Lactams via Olefin Difunctionalization: Iridium Nitrenoids as a Motif of LUMO-Controlled Dipoles
摘要:
Reported herein is a general platform of a stereodefined access to gamma-lactams via Cp*Ir-catalyzed olefin difunctionalization, where in situ generated Ir-nitrenoid is utilized as a key motif of 1,3-dipoles to enable amido transfer in a syn-selective manner. Computational studies suggested that the stereodefined process can be attributed to the proposed working mode of concerted [3 + 2] cyclization. Frontier molecular orbital (FMO) analysis implied that a low-lying lowest unoccupied molecular orbital (LUMO) of the Ir-imido fragment engages in the olefin interaction. Mechanistic understanding on the nitrene transfer process led us to develop mild catalytic protocols of stereoselective difunctionalization of alkenyl dioxazolones to furnish alpha-(haloalkyl)- or (oxyalkyl)lactam products which are of high synthetic and medicinal utility. Product stereochemistry (threo and erythro) was found to be designated by the olefin geometry (E/Z) of substrates.
作者:Daniel H. Paull、Chao Fang、James R. Donald、Andrew D. Pansick、Stephen F. Martin
DOI:10.1021/ja305117m
日期:2012.7.11
highly enantioselectivebromolactonizations of a number of structurally distinct unsaturated acids. Like some known catalysts, this catalyst promotes highly enantioselectivebromolactonizations of 4- and 5-aryl-4-pentenoic acids, but it also catalyzes the highly enantioselectivebromolactonizations of 5-alkyl-4(Z)-pentenoic acids. These reactions represent the first catalytic bromolactonizations of alkyl-substituted
Enantioselective Halolactonization Reactions using BINOL-Derived Bifunctional Catalysts: Methodology, Diversification, and Applications
作者:Daniel W. Klosowski、J. Caleb Hethcox、Daniel H. Paull、Chao Fang、James R. Donald、Christopher R. Shugrue、Andrew D. Pansick、Stephen F. Martin
DOI:10.1021/acs.joc.8b00490
日期:2018.6.1
A general protocol is described for inducing enantioselective halolactonizations of unsaturated carboxylic acidsusing novel bifunctional organic catalysts derived from a chiral binaphthalene scaffold. Bromo- and iodolactonization reactions of diversely substituted, unsaturated carboxylic acids proceed with high degrees of enantioselectivity, regioselectivity, and diastereoselectivity. Notably, these
Intermolecular Heck Coupling with Hindered Alkenes Directed by Potassium Carboxylates
作者:Tucker R. Huffman、Yebin Wu、Alexis Emmerich、Ryan A. Shenvi
DOI:10.1002/anie.201813233
日期:2019.2.18
Pd0 -catalyzed Mizoroki-Heck reactions traditionally exhibit poor reactivity with polysubstituted, unbiased alkenes. Intermolecular reactions with simple, all-carbon tetrasubstituted alkenes are unprecedented. Herein we report that pendant carboxylic acids, combined with bulky monophospine ligands on palladium, can direct the arylation of tri- and tetrasubstituted olefins. Quaternary carbons are established
alkenyl C–H allylation by an exo-palladacycle intermediate is demonstrated, employing unactivated (Z)-alkenes and allyl carbonates. With the use of an 8-aminoquinoline (AQ) derived amide as the directing group, the N,N-bidentate-chelation-assisted C–H activation protocol proceeded under mild and oxidant-free conditions with excellent selectivity. The utility of this approach is demonstrated by the preparative
Enantioselective Iodolactonization of Disubstituted Olefinic Acids Using a Bifunctional Catalyst
作者:Chao Fang、Daniel H. Paull、J. Caleb Hethcox、Christopher R. Shugrue、Stephen F. Martin
DOI:10.1021/ol3030555
日期:2012.12.21
The enantioselectiveiodolactonizations of a series of diversely substituted olefinic carboxylic acids are promoted by a BINOL-derived, bifunctional catalyst. Reactions involving 5-alkyl- and 5-aryl-4(Z)-pentenoic acids and 6-alkyl- and 6-aryl-5(Z)-hexenoic acids provide the corresponding γ- and δ-lactones having stereogenic C–I bonds in excellent yields and >97:3 er. Significantly, this represents
BINOL 衍生的双功能催化剂促进了一系列不同取代的烯烃羧酸的对映选择性碘内酯化。涉及 5-烷基-和 5-芳基-4( Z )-戊烯酸和 6-烷基-和 6-芳基-5( Z )-己烯酸的反应提供相应的具有立体异构 C-I 键的 γ-和 δ-内酯以优异的产量和 >97:3 er。值得注意的是,这代表了第一种以高对映选择性促进溴和碘内酯化的有机催化剂。还证明了该催化剂诱导外消旋不饱和酸的动力学拆分的潜力。