Synthesis and antibacterial activity of C4 substituted monobactams
摘要:
The synthesis and antibacterial activity of a series of monobactams having various substituents at C4 position is described. An efficient route to versatile intermediates 4a-c from 6-aminopenicillanic acid (6-APA) has been developed. Derivatives 10e, 11, 21 showed good to moderate activity against Gram-negative bacteria with the exception of Pseudomonas aeruginosa. Introduction of a catechol moiety on the C4 side chain only slightly improved the activity against P aeruginosa.
A fair exchange: In the title reaction, alkynyllithium serves as an initiator for benzyne generation through an iodine–lithium exchange (see scheme; Tf=trifluoromethanesulfonyl). When performed in the presence of stoichiometric amounts of a nucleophile, the generated benzyne undergoes attack by lithio nucleophiles to generate aryllithium, which is then iodinated by iodoalkyne to give the iodoarenes
Thieme Chemistry Journal Awardees - Where
Are They Now? Aerobic Oxidative Coupling of Tertiary Amines
with Silyl Enolates and Ketene Acetals
作者:Martin Klussmann、Devarajulu Sureshkumar、Abhishek Sud
DOI:10.1055/s-0029-1217336
日期:——
Cyclic tertiary amines can be oxidatively coupled with a variety of silyl enol ethers or ketene acetals to furnish tertiary Mannich bases. The reactions are catalyzed by simple copper salts employing elemental oxygen as the oxidant.
and Michael reactions of silyl enol ethers with carbonyl compounds or other electrophiles (trimethyl orthoformate, dimethyl acetal, and chloromethyl methyl ether), the allylation reaction of allylsilanes with aldehydes, and the Diels–Alder reaction of dienes with α,β-unsaturated aldehydes. A solution of formaldehyde in water is applicable as an electrophile. Also, the aldol-type reaction of ketene silyl
Rhenium-catalyzed reaction of carbonyl compounds with ketene silyl acetals
作者:Yutaka Nishiyama、Kenta Kaiba、Rui Umeda
DOI:10.1016/j.tetlet.2009.11.109
日期:2010.2
It was found that rhenium complex is an effective catalyst for the reaction of carbonyl compounds with ketene silyl acetals. A wide range of β-silyloxy esters is obtained by the treatment of carbonyl compounds with ketene silyl acetals in the presence of a catalytic amount of ReBr(CO)5 in moderate to good yields.
Direct Mannich-Type Reactions Promoted by Frustrated Lewis Acid/Brønsted Base Catalysts
作者:Jessica Z. Chan、Wenzhi Yao、Brian T. Hastings、Charles K. Lok、Masayuki Wasa
DOI:10.1002/anie.201608583
日期:2016.10.24
Direct Mannich‐type reactions that afford both α‐ and β‐amino esters by the reaction of a broad range of carbonyl compounds and aldimines are disclosed. The transformation is promoted by a sterically frustrated Lewis acid/Brønsted base pair, which is proposed to operate cooperatively: Within the catalyst complex, an enolate is generated that then reacts with a hydrogen‐bond‐activated imine. Noncovalent