Amides trapping reagents

C.viii. Amines, Amides, Imides, and Sulfonamides as the H—Y Trapping Reagents Intermolecular Diene Dimerization... 

For example, Chang s group used simple amines [55], alcohols [56], and water [57] as trapping reagents to perform three-component reactions, obtaining amidates 86, imidates 87, and amides 88, respectively (Scheme 5.57). 

Conversions of carboxylic acids to ketones are typically performed in stepwise fashion6 via intermediates such as acid chlorides,7 anhydrides,8 thioesters,9 or N-alkoxy amides,10 or by the direct reaction of carboxylic adds with lithium reagents.11 In this latter method trimethylsifyl chloride has been shown to be an effective reagent for trapping the tetrahedral alkoxide intermediates and for quenching excess organolithium reagent. 

Monoaddition to esters. The reagent formed from RMgX and LDA (1 1) reacts with esters or amides to give enolates of ketones, which can be trapped by ClSi(CH,)v This technique provides a synthesis of artemisia ketone (1) by an aldol... 

An alternate step-wise cyclization strategy to form 3-carboline 22 is shown in Scheme 7. Acylation of D-tryptophan (21) with piperonyloyl chloride afforded amide 25, which was converted to thioamide 26 with Lawesson s reagent. Thioamide 26 was treated with methyl iodide in refluxing CH2CI2 to give a a-thiomethylimmonium ion, which was trapped by the intramolecular addition of indole. The thiomethyl group was... 

In one important series of compounds, the mono-halocyclopropane is generated in situ from a 1,3-dehydrohalogenation of a l,3-dihalopropan-2-one acetal using a metal amide with an excess of reagent, the cyclopropene produced in metallated in situ and can be further functionalized by trapping with electrophiles48 ... 

In addition to protonic acids, Lewis acids are the most common initiators of carbocationic polymerizations. Two mechanisms are possible. Direct initiation is rare and usually slow. The more prevalent mechanism is by cocatalysis in binary systems, with the Lewis acid acting as a coinitiator or catalyst rather than as initiator. Cationating or protonating species are the true initiators, which are therefore the species incorporated at the polymer s end group. The most common initiator is adventitious water in insufficiently dried systems. Thus, mechanistic studies should be performed under stringently dry conditions or in the presence of proton traps such as hindered pyridines. In addition to water, the protonating reagent may be an alcohol, carboxylic acid, amine, or amide [Eq. (28)]. 

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