In the second route the functionalized alkyne 15 was prepared by enantioselective alkylation of cumyl ester protected glycine imine 17 and propargyl bromide18, in the presence of phase transfer catalyst 19 (ee = 96%) (). Then, hydrolysis of the imine function and cleavage of the cumyl ester was done by hydrogenolysis in methanol, while maintaining the acid labile acetylene protecting group (TES). After removal of both protecting groups, formation of the methyl ester with TMSCl in methanol followed by protection of the amino group gave propargyl glycine 15 in an overall yield of 71% (3 steps). Initially we used a tert-butyl ester group in glycine imine 17, but the deprotection with TMSCl took 3 d, and was accompanied by partial cleavage of the TES.
A classical route to N-methylamino acids is to start from the amino acid, protect the amino group as a carbamate and then to methylate the dianion, for example with NaH/CH3I in DMF., However in the case of tryptophan this strategy requires protection of the indole NH prior to the N-methylation step. The same is true for other side chain functionalized amino acids. An alternative that avoids protection of the indole NH is via sequential reductive amination, first with benzaldehyde then with paraformaldehyde, followed by debenzylation through catalytic hydrogenation and urethane formation. In addition, the reduction of formamide derivatives has been used as a means of N-methylation.
15/04/2001 · Oxalyl Chloride–Dimethylformamide
Thionyl chloride dehydrates primary amides to form nitriles (eq 8); for example, 2-ethylhexanonitrile is produced in about 90% yield by heating with SOCl in benzene. Substituted benzonitriles are readily produced from benzamides. These reactions may also be catalyzed by DMF. -Alkylformamides may be dehydrated to isocyanides.Treatment of -alkyl or -aryl secondary amides with thionyl chloride in an inert solvent such as methylene chloride results in the formation of imidoyl chlorides (eq 9). Upon heating, the imidoyl chlorides from -alkylamides undergo scission to generate nitriles and alkyl chlorides via the von Braun degradation (eq 10).Aromatic or ,-unsaturated aldehydes or their bisulfite addition compounds are converted to -dichlorides by treatment with SOCl, either neat or in an inert solvent such as nitromethane (eq 11). This process is readily catalyzed by HMPA. Thionyl chloride may be preferred over the more commonly used PCl if removal of byproducts is problematic with the latter reagent.
December « 2017 « New Drug Approvals
One procedure involves the sequential addition of thionyl chloride and then the acid to chilled methanol. Alternatively, benzyl esters have been prepared by the slow addition of SOCl to a suspension of the amino acid in benzyl alcohol at 5 °C.For the formation of acid chlorides, the competing reactions of concern are -oxidation and acid-catalyzed degradation.
May « 2017 « New Drug Approvals
Both symmetrical [R1R2C(OR3)] and mixed [R1R2C(OR3)OR4] acetals can be obtained, depending upon the choice of conditions.The three equilibria shown in eqs 1-3 are established when 2,2-dimethoxypropane, an alcohol, and a catalytic amount of acid are mixed.
10 posts published by DR ANTHONY MELVIN CRASTO Ph.D during May 2017
(+)-Camphorsulfonyl chloride is produced in 99% yield without a catalyst. Use of the salts of sulfinic acids minimizes their oxidation; -toluenesulfinyl chloride is produced in about 70% yield from sodium -toluenesulfinate dihydrate with excess thionyl chloride. is more commonly used for this transformation.
Oxygen is a chemical element with symbol O and atomic number 8
As shown in eq 14, catalysis yields symmetric sulfoxides, while in the absence of Lewis acids, aromatic thiosulfonates are the principal products. Primary amines, especially aromatic ones, react with SOCl to produce -sulfinylamines, which are potent enophiles and useful precursors to some heterocyclic compounds.