Organocerium reactions of benzamides and thiobenzamides: A direct synthesis of tertiary carbinamines

Calderwood, David J.; Davies, Roy V.; Rafferty, Paul; Twigger, Helen L.; Whelan, H. M.

doi:10.1016/s0040-4039(97)00047-6

Cited by 30 publications

(5 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Finally, Calderwood and co‐workers reported the addition of MeCeCl 2 to unsubstituted (thio)benzamides 151 to give tertiary carbinamines 152 (Scheme ). Presumably, the strong Ce‐oxophilicity61 triggers the dehydration of (thio)benzamides to the corresponding nitriles 155 , which then undergo attack of the methyl nucleophile 87…”

Section: Synthesis Of Amines or Imines Via Addition Of Organometallmentioning

confidence: 99%

Increasing the Reactivity of Amides towards Organometallic Reagents: An Overview

2014

View full text Add to dashboard Cite

The nucleophilic addition of carbon nucleophiles to amides has traditionally been a difficult task, both due to reactivity and selectivity problems. When successful, these processes would represent straightforward routes towards carbonyl‐type or amine compounds, depending on the fate of the generated tetrahedral intermediate. The direct addition of nucleophiles to amides for the preparation of ketones has been studied and applied to the syntheses of several natural products. On the other hand, the addition of nucleophiles to amides to obtain substituted amines represented a major challenge, and only scattered applications on particular substrates have appeared. Initial improvements were based on the activation of amides by introduction of particular substituents, such as in N‐methoxy amides (Weinreb amides) or electron‐withdrawing groups able to increase the carbon nucleophilicity. Although these strategies facilitate the introduction of nucleophiles, chemoselectivity issues arise when additional electrophilic moieties (i.e., carbonyls) are present, thus decreasing the versatility of the methods. In recent years, important advancements towards fully chemoselective methods have been realized. The capture of tetrahedral intermediates with acids generates highly electrophilic iminium species able to undergo chemoselective additions of various nucleophiles, thus accessing substituted amines. Alternatively, the in situ generation of an iminium triflate ion allows highly chemoselective additions of nucleophiles, yielding amines, ketones or ketimines. Also thioamides can be used as precursors of ketones or α‐substituted amines. The success of the above methodologies is further showcased by the application in various syntheses of natural products or biologically active molecules.

show abstract

Section: Synthesis Of Amines or Imines Via Addition Of Organometallmentioning

confidence: 99%

Increasing the Reactivity of Amides towards Organometallic Reagents: An Overview

2014

View full text Add to dashboard Cite

show abstract

“…The direct transformation of amides to other classes of compounds has attracted considerable attention in recent years. − However, in contrast to the many methods developed for the transformation of common tertiary and secondary amides, the direct transformation of primary amides involving C–C bond formation is rare . To the best of our knowledge, only the reductive alkylation of primary amides has been reported, which involves the one-pot dehydration of benzamides with organocerium reagents to benzonitriles and subsequent nucleophilic addition to give tertiary carbinamines …”

Section: Introductionmentioning

confidence: 99%

One-Pot Reductive 1,3-Dipolar Cycloaddition of Secondary Amides: A Two-Step Transformation of Primary Amides

Huang

Lang

2016

J. Org. Chem.

View full text Add to dashboard Cite

The one-pot reductive 1,3-dipolar cycloaddition of secondary aromatic N-(trimethylsilylmethyl)amides with reactive dipolarophiles is reported. The method relies on the in situ generation of nonstabilized NH azomethine ylide dipoles via amide activation with triflic anhydride, partial reduction with 1,1,3,3-tetramethyldisiloxane (TMDS), and desilylation with cesium fluoride (CsF). Running under mild conditions, the reaction tolerated several sensitive functional groups and provided cycloadducts in 71-93% yields. The use of less reactive dipolarophile methyl acrylate led to the cycloadduct in only 40% yield. A (Z) geometric intermediate of NH-azomethine 1,3-dipole was postulated to account for the observed higher yields and higher cis diastereoselectivity for the substrates bearing an electron-withdrawing group. This model features an unconventional cyclic transition state via carbanion-aryl ring interaction. Because the starting secondary amides can be prepared from common primary amides, the current method also constitutes a two-step transformation of primary amides.

show abstract

“…[11][12][13] ii) Reactions of cyanide ion with: A) activated pyridine Noxides; [14][15][16][17][18] B) N-alkyl; 19 C) N-acyl-pyridinium cations; 14 D) N-aminopyridinium cations; 20 E) 2-halopyridines. 21 iii) Dehydration, decarboxylation and/or oxidation of: A) primary amides; 22,23 B) primary alcohols; 24,25 C) 2-pyridylacetic esters, oximinocarbonates and carbamates; 26 D) pyridine-2-aldehyde and 2-acylpyridine N,N-dimethylhydrazones; 27 E) dehydration of pyridine-2-oximes. [28][29][30][31][32][33] The parent 2-, 3-and 4-cyanopyridines are themselves each produced on an industrial scale in large quantities by ammoxidation of the corresponding picolines.…”

mentioning

confidence: 99%

Preparation of Cyanopyridines by Direct Cyanation

Katritzky¹,

Scriven²,

Majumder³

et al. 2005

Synthesis

View full text Add to dashboard Cite

After pretreatment with nitric acid and trifluoroacetic anhydride, aqueous potassium cyanide converted pyridines 1a-l into their corresponding 2-cyano derivatives 4a-l in an average yield of 52%.Cyanopyridines are widely used in the preparation of the corresponding acids, 1,2 aldehydes, 3,4 ketones, 5 and as important synthetic intermediates for the synthesis of herbicides, pesticides, fungicides, 6 and pharmaceuticals. 7 Some substituted cyanopyridines are themselves biologically active. 6 2-Cyanopyridine is also useful as starting material for complex heterocyclic compounds. 8,9 Three main approaches are currently available for the preparation of 2-cyanopyridines (Scheme 1):i) Ammoxidation of A) 2-methylpyridines; 7,10 B) pyridine 2-aldehydes. [11][12][13] ii) Reactions of cyanide ion with: A) activated pyridine Noxides; 14-18 B) N-alkyl; 19 C) N-acyl-pyridinium cations; 14 D) N-aminopyridinium cations; 20 E) 2-halopyridines. 21 iii) Dehydration, decarboxylation and/or oxidation of: A) primary amides; 22,23 B) primary alcohols; 24,25 C) 2-pyridylacetic esters, oximinocarbonates and carbamates; 26 D) pyridine-2-aldehyde and 2-acylpyridine N,N-dimethylhydrazones; 27 E) dehydration of pyridine-2-oximes. [28][29][30][31][32][33] The parent 2-, 3-and 4-cyanopyridines are themselves each produced on an industrial scale in large quantities by ammoxidation of the corresponding picolines. However, this method shows poor selectivity with respect to a particular methyl group when applied to lutidines and it is not applicable to most functionalized methylpyridines. Scheme 1Downloaded by: University of Queensland. Copyrighted material.

show abstract

Organocerium reactions of benzamides and thiobenzamides: A direct synthesis of tertiary carbinamines

Cited by 30 publications

References 7 publications

Increasing the Reactivity of Amides towards Organometallic Reagents: An Overview

Increasing the Reactivity of Amides towards Organometallic Reagents: An Overview

One-Pot Reductive 1,3-Dipolar Cycloaddition of Secondary Amides: A Two-Step Transformation of Primary Amides

Preparation of Cyanopyridines by Direct Cyanation

Contact Info

Product

Resources

About