Ester Cleavages via S _N 2‐Type Dealkylation

Abstract

The cleavage of esters to furnish carboxylic acids is a common organic transformation that is usually carried out in a routine manner by acidic or basic hydrolysis. It often happens, however, particularly in the synthesis of natural products, that the substrate ester is sensitive to hydrolytic conditions. For such sensitive materials a number of mild, neutral methods of ester cleavage have been devised. Those methods that occur with displacement of carboxylate by SN2 dealkylation are the subject of this chapter.

Palladium-Catalyzed 1,1-Alkynyloxygenation of 2-Vinylbenzoates with Alkynyl Bromides

“…As a result, the corresponding 1,1-alkynyloxygenation product 3a and 1-(2-bromoethyl)­naphthalene 7 were obtained in 60 and 62% isolated yields, respectively (Scheme ). This result indicates that the attack of a bromine anion on the alkyl carbon atom is presumably involved in the cleavage of the C­(alkyl)–O bond . This mechanistic hypothesis is consistent with the observation that 1,1-alkynyloxygenation of the phenyl ester 1f did not occur under the standard conditions (Table , entry 5).…”

Radical Decomposition of Ether-Based Electrolytes for Li-S Batteries

“…17 Sulfides and polysulfides are known for their high nucleophilicity, in part due to the large atomic volume of sulfur, making them readily polarizable. Organic thiolates, which have a negatively charged sulfur atom analogous to sulfides and polysulfides, have been shown to be highly reactive toward organic esters, 18 resulting in their cleavage. Therefore it is not unlikely that polysulfides formed during discharge of sulfur cathodes can also react with organic carbonates via nucleophilic attack, 4 forming (poly)-thioesters.…”

“…In fact, this might be one of the reasons for the early reports on DOL-containing electrolytes offering better performance, 3,30,31 as those did not use SEI forming additives (e.g., LiNO 3 ). 32 The presence of ethyl formate appears to be, however, very detrimental to the cell cycling life, since polysulfides can react with esters, 4,18 forming electrochemically inert products. According to the above-mentioned processes, Figure 5 shows the proposed mechanism which could explain the higher capacity observed in the sloping region (Figures 1 and 2).…”

Dealkylation of Poly(methyl methacrylate) by TiCl4 Vapor Phase Infiltration (VPI) and the Resulting Chemical and Thermophysical Properties of the Hybrid Material

“…Interestingly, this proposed mechanism results in a residual carbonyl group, consistent with IR and XP spectroscopic observations, and the small to negligible shift in the C–O–R vibration in IR spectroscopy is consistent with the similar vibrational frequencies reported for both C–O–R and C–O–M species . In general, the alkyl cleavage of esters to form carboxylic acids is well documented in the literature. − This process commonly occurs by acid- or base-catalyzed hydrolysis of esters following a concerted dealkylation mechanism. Reports exist for alkyl cleavage of esters via strong Lewis acids such as AlCl 3 , TiCl 4 , or other metal halides as a catalyst in the presence of another co-reactant. , However, to our knowledge, no reports exist for dealkylation of esters in polymers using gaseous metal halides in low vapor pressure environments.…”

“… 39 In general, the alkyl cleavage of esters to form carboxylic acids is well documented in the literature. 42 − 45 This process commonly occurs by acid- or base-catalyzed hydrolysis of esters following a concerted dealkylation mechanism. Reports exist for alkyl cleavage of esters via strong Lewis acids such as AlCl 3 , TiCl 4 , or other metal halides as a catalyst in the presence of another co-reactant.…”