“…Carboalkoxylation of organic halides gives the homologated esters by the use of a catalytic amount of transition metal complexes. While much has been learned preparing the methyl, ethyl, and n -butyl esters as a carboalkoxylation product, to our knowledge very few studies have been performed on the synthesis of the tert -butyl esters, , which act as an easily removable O -protecting group. One serious drawback to the transition-metal-catalyzed carboalkoxylation of organic halide is the structural restriction, especially of the reactant alcohols.…”
Section: Introductionmentioning
confidence: 99%
“…One serious drawback to the transition-metal-catalyzed carboalkoxylation of organic halide is the structural restriction, especially of the reactant alcohols. Actually, methanol, butanol, and benzyl alcohol can be used and gave the corresponding esters in good yield, whereas with tertiary alcohols, the carbonylation did not work well, probably as a result of steric hindrance of the alcohol nucleophiles. , For example, Tanaka 15a and Watanabe 15b reported that the reactions of organic halides with tert -butyl alcohol under pressure of CO at high temperature gave the corresponding esters 1 − 3 in poor yields (Scheme ). 1 …”
A modification and details of the palladium-catalyzed tert-butoxycarbonylation of 2,2,2-trifluoroacetimidoyl iodides 1, which gave the iminocarboxylates 2, one of the promising precursors to fluorinated alpha-amino acids, are described. The Pd-catalyzed carbonylation reaction was remarkably promoted by the use of DMF or DMI as an additive, enough to achieve the selective formation of tert-butyl iminoesters. Nucleophilic alkylation of the imine moiety of 2 and subsequent removal of N- and O-protecting groups gave a variety of 2-substituted 2-amino-3,3,3-trifluoropropanoic acid derivatives 3 in high yields.
“…Carboalkoxylation of organic halides gives the homologated esters by the use of a catalytic amount of transition metal complexes. While much has been learned preparing the methyl, ethyl, and n -butyl esters as a carboalkoxylation product, to our knowledge very few studies have been performed on the synthesis of the tert -butyl esters, , which act as an easily removable O -protecting group. One serious drawback to the transition-metal-catalyzed carboalkoxylation of organic halide is the structural restriction, especially of the reactant alcohols.…”
Section: Introductionmentioning
confidence: 99%
“…One serious drawback to the transition-metal-catalyzed carboalkoxylation of organic halide is the structural restriction, especially of the reactant alcohols. Actually, methanol, butanol, and benzyl alcohol can be used and gave the corresponding esters in good yield, whereas with tertiary alcohols, the carbonylation did not work well, probably as a result of steric hindrance of the alcohol nucleophiles. , For example, Tanaka 15a and Watanabe 15b reported that the reactions of organic halides with tert -butyl alcohol under pressure of CO at high temperature gave the corresponding esters 1 − 3 in poor yields (Scheme ). 1 …”
A modification and details of the palladium-catalyzed tert-butoxycarbonylation of 2,2,2-trifluoroacetimidoyl iodides 1, which gave the iminocarboxylates 2, one of the promising precursors to fluorinated alpha-amino acids, are described. The Pd-catalyzed carbonylation reaction was remarkably promoted by the use of DMF or DMI as an additive, enough to achieve the selective formation of tert-butyl iminoesters. Nucleophilic alkylation of the imine moiety of 2 and subsequent removal of N- and O-protecting groups gave a variety of 2-substituted 2-amino-3,3,3-trifluoropropanoic acid derivatives 3 in high yields.
“…However, a literature survey regarding carbonylation reactions of indoles revealed that, despite the usefulness of carboxylated indoles, there was no such reaction of easily available bromoindoles reported. Also, other types of palladium-catalyzed coupling reactions of unprotected haloindoles are rare . One of the possible reasons for the lack of these reactions is the presence of the acidic NH proton and the possibility of the haloindole to oligomerize or polymerize in the presence of a palladium catalyst.…”
[reaction: see text] For the first time, palladium-catalyzed carbonylations of unprotected bromoindoles have been performed successfully with different N- and O-nucleophiles. Various indole carboxylic acid derivatives are accessible in excellent yield. For example, aminocarbonylation of 4-, 5-, 6-, or 7-bromoindole with arylethylpiperazines provides a direct one-step synthesis for CNS active amphetamine derivatives.
“…The ratio of the two isomers was about 2.5/1. When we submitted the major isomer to palladium-catalyzed carbonylation under standard conditions, an unexpected product, lactone 6 , was isolated quantitatively. The formation of 6 implied that deprotection of the Cbz group and lactonization occurred simultaneously under these conditions.…”
Heating a mixture of alpha-aryl ketone with (R)-phenylglycinol produces a mixture of imine and 1,3-dioxazolidine. Treatment of this mixture with trimethylsilyl cyanide followed by transformation of nitrile to ester gives Strecker-type reaction products. The diastereoselectivity of the generated alpha-amino esters is from 2/1 to 7/1, and the (R,S)isomer is found as the major product. The (R,S) and (R,R)isomers can be separated by conversion to their N-Cbz or cyclization derivatives. Using this methodology, four antagonists of metabotropic glutamate receptors, (S)-alphaM4CPG, (S)-MPPG, (S)-AIDA, and (S)-APICA, are synthesized.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
