Preparation of dialkyl carbonates via the phase-transfer-catalyzed alkylation of alkali metal carbonate and bicarbonate salts

Roles of Bases in Transition-Metal Catalyzed Organic Reactions

“…Figure 9 Base assisted concerted metalation/deprotonation Shaw 等在 70 年代早期发现, 向反应体系中添加醋 酸钠可以促进 Ir [15] , Pt [16] , Pd [17] 配合物的环金属化反应. 例如在图 10 的反应中, 当没有碱加入时, 只能得到钯与 底物 7 的普通加合物 PdCl 2 (7) 2 , 而在加入 1 equiv.的碱 后, 则能顺利反应以 84%的收率得到钯杂五元环产物 8 [17] . [17,18] Figure 10 Effect of NaOAc on the cyclopalladation [17,18] 过渡金属催化的反应中也有类似的过程.…”

“…碱的去质子化 能力与其 pK a 值(无机碱的共轭酸的 pK a 值)及其在相应 溶剂中的溶解度有着十分紧密的联系. 对不同碱在不同有机溶剂中的溶解度进行专门研 究的文献极少(表 1) [2] . 无机碱在有机溶剂中的碱性并不 好衡量(图 2) [3] , 这是因为大部分的无机碱在有机溶剂中 的溶解性都不是很好, 同时, 所使用的溶剂和金属离子 在溶剂中的聚集度也会对碱的性质带来影响.…”

Unexpected Squaramide‐Induced Cleavage of Benzils: Synthesis and Characterization of Mono‐Aroyl Squarimides

“…To avoid the formation of products originating from the benzilic acid rearrangement and/or the basic hydrolysis of SQ 2a, we choose to use Cs 2 CO 3 in anhydrous DMF as the reaction medium. [13] Cesium carbonate in DMF solution is basic enough to cause a partial deprotonation of SQ and promote the nucleophilic attack of the SQ 2a anion on one of the carbonyl groups of the benzils. To our surprise, the reaction of 4,4-dimethylbenzil 1a and SQ 2a under the selected initial conditions (r.t., 96 h, anhydrous DMF, Ar balloon) afforded the mono-aroyl squarimide 3a that was isolated as a solid in 37 % yield simply by filtration (Table 1, entry 1).…”

“…Supporting Information (see footnote on the first page of this article): Characterization data for compounds 3a-3d and 4a-4d, copies of 1 H, 13 C and 2D NMR spectra, HPLC traces, UV/Vis conditions for pK a calculations.…”

Synthesis of Linear and Cyclic Carbonates

“…The alkylation reaction of various alkali and alkaline -earth metal carbonates with alkyl halides R(CH 2 )nX (X = Cl, Br, I) is a primary synthetic procedure in organic chemistry for obtaining various symmetrical and unsymmetrical dialkyl carbonates under phase -transfer conditions in polar aprotic solvents [45] . Excellent yields may be obtained by running the reaction at 383 K in ionic liquids such as imidazolium salts, offering the advantage of simple experimental and work -up procedures [46] .…”