Carbinolamine intermediates

Isolation of the carbinolamine intermediate (66) is possible in the reaction of 2-amino-5-nitrothia2ole with acetaldehyde (Scheme 46) (216). 

Write the structure of the carbinolamine intermediate and the imine product formed in the reaction of each of the following... 

Reaction with secondary amines (Sec tion 17 11) Isolated product IS an en amine Carbinolamine intermediate can not dehydrate to a stable imine... 

Imines are formed by nucleophilic addition of a primary amine to the carbonyl group of an al dehyde or a ketone The key step is formation of a carbinolamine intermedi ate which then dehy drates to the imine... 

General acid catalysis of the breakdown of the carbinolamine intermediate occurs by assistance of the expulsion of water. 

Reaction with primary amines (Section 17.10) Isolated product is an imine (Schiff s base). A carbinolamine intermediate is formed, which undergoes dehydration to an imine. 

Stop-flow conditions that carbinolamine intermediate 4 dehydrates to form syn and anti oximes. The syn isomer 5 cyclized within several minutes to 3, while conversion of the anti form required several hours. 

The key step is nucleophilic addition to yield a carbinolamine intermediate, which then loses water to give the imine. 

J. K. Baker, T. L. Little, Metabolism of Phencyclidine. The Role of the Carbinolamine Intermediate in the Formation of Lactam and Amino Acid Metabolites of Nitrogen Heterocycles , J. Med. Chem. 1985, 28, 46-50. 

Torisawa [17] developed an alternative oxidative amidation of aldehydes using palladium chloride (PdCl2)-xantphos complex as a catalyst. The use of hydrogen peroxide (H2O2)-urea complex as oxidant prevents the formation of imine from the carbinolamine intermediate and minimizes the level of benzoic acid side... 

Secondary amines are compounds of the type R2NH. They add to aldehydes and ketones to form carbinolamines, but their carbinolamine intermediates can dehydrate to a stable product only in the direction that leads to a carbon-carbon double bond ... 

Electroanalytical techniques indicate the formation of two carbinolamine intermediates and one monohydrazone in the reaction of terephthalaldehyde with hydrazine at pH 7.3.91... 

Oxidative amidation of aldehydes can be achieved with primary amine hydrochlorides, Cul as catalyst, and r-BuOOH as oxidant, probably via a carbinolamine intermediate.343... 

The intermediate results from the addition of an amine to a ketone. The product is an enamine because the amine nitrogen in the carbinolamine intermediate comes from a secondary amine. 

Hofmann rearrangement (the mechanism is shown in Section 24.6) of an a-hydroxy amide produces a carbinolamine intermediate that expels ammonia to give an aldehyde. 

In the early 1960s, seminal work by Jencks and coworkers demonstrated that formation and hydrolysis of C=N bonds were proceeding via a carbinolamine intermediate, thus leading to a more general mechanism of addition reactions on carbonyl groups [17-19]. The dynamic nature of the reaction of imine formation can be exploited to drive the equilibrium either forward or backwards. Since the reaction involves the loss of a molecule of water, adding or removing water from the reaction mixture proved an efficient way to shift the equilibrium in either direction. The responsive behavior of imines to external stimuli makes the reversible reaction of imine formation perfectly suited for DCC experiments [20], Thermodynamically controlled reactions based on imine chemistry include (1) imine condensation/hydrolysis, (2) transiminations, and (3) imine-metathesis reactions... 

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