N-Heterocyclic Carbene-Catalyzed <i>in situ</i>
Activation of Alkynyl Acids for C−S Bond Formation: Access to Imidazo[2,1-<i>b</i>
][1,3]thiazinones
作者:Kewen Sun、Shiyi Jin、Jindong Zhu、Xinmiao Zhang、Maoyu Gao、Wanqi Zhang、Tao Lu、Ding Du
DOI:10.1002/adsc.201800857
日期:2018.12.3
Alkynylacids are first utilized as alkynyl acylazolium precursors through an in situactivation strategy for the efficient construction of carbon‐sulfur bond in a formal [3+3] annulation. This protocol offers a direct and rapid pathway for the synthesis of imidazo[2,1‐b][1,3]thiazinone skeleton, a useful heterocyclic class frequently found in many bioactive compounds. This reaction also has the advantages
炔酸首先通过原位活化策略用作炔基酰基la唑前体,以便在正式的[3 + 3]环空中有效构建碳硫键。该方案为合成咪唑并[2,1– b ] [1,3]噻嗪酮骨架提供了直接而快速的途径,该骨架是在许多生物活性化合物中经常发现的有用的杂环类。该反应还具有可扩展性,易于获得的材料以及在露天中易于操作的优点。
two-step intermolecular esterification via the condensation of carboxylic acids with nucleophilic hydroxyl species was reported. A broad substrate scope with respect to carboxylic acids, alcohols, and phenols was observed. The α-acyloxyenamide intermediates formed by the addition of carboxylic acids to ynamides proved to be effective acylating reagents for the esterification of alcohol and phenol derivatives
Esters as Alkynyl Acyl Ammonium and Azolium Precursors: A Formal [2 + 3] Annulation with Amidomalonates via Lewis Base/Lewis Acid Cooperative Catalysis
作者:Jing Cao、Kewen Sun、Shuding Dong、Tao Lu、Ying Dong、Ding Du
DOI:10.1021/acs.orglett.7b03453
日期:2017.12.15
Esters are for the first time used as α,β-unsaturated alkynyl acyl ammonium and azolium precursors to undergo a formal [2 + 3] annulation with amidomalonates through DMAP/LiCl or carbene/LiCl cooperative catalysis. A wide range of (Z)-5-amino-3-furanones were obtained in moderate to high yields with high regioselectivity and stereoselectivity. In addition, a plausible mechanism based on the calculated
With the aim of developing novelannulationsvia ketene intermediates, allenyl imide and alkynoates bearing good leaving groups are used for their function in a tandem conjugate addition–elimination reaction (SN2′ type) promoted by nucleophilic phosphine catalysts. By utilizing thioamides as 1S,3N-bis-nucleophiles, [3+3] and [3+2] annulations have been established to allow rapid access to 1,3-thiazin-4-ones