Chemoselective Addition of Hydrazine to δ‐Keto Esters and Dimethylformamide‐Mediated Deesterification

Saravanan, Sivaperuman; Sridharan, Vellaisamy; Muthusubramanian, Shanmugam

doi:10.1080/00397910500464319

Cited by 4 publications

(4 citation statements)

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“…azole, and other carbonyl compounds. 8 Moreover, the yield of most of the semicarbazones achieved by using such synthetic techniques is poor. Garland et al also reported the preparation of semicarbazone and hydrazone derivatives from common semicarbazones and hydrazones, respectively, via imino-isocyanates, wherein various amines and anilines were used as nucleophiles with hydrazones.…”

Section: Syn Thesismentioning

confidence: 99%

“…For instance, it was extremely troublesome to obtain N 4 -(alkoxycarbonylphenyl) semicarbazones starting from the ester substituted phenyl amine because of the high reactivity of hydrazine towards the ester moiety in the second step. 8 To examine the versatility of this method, three benzaldehydes having electron-donating and electron-withdrawing groups were used. We carried out this reaction with m-anisaldehyde, 4-fluorobenzaldehyde, and cuminaldehyde to prepare semicarbazones containing different substituents on the N 1 -benzylidene ring under the same reaction conditions; the results are outlined in Scheme 5.…”

Section: Syn Thesismentioning

confidence: 99%

“…The observation that (3,5-di-tert-butyl-4-hydroxybenzylsulfanyl)acetic acid ethyl ester (8) was found as a reaction product along with semicarbazones in every reaction, indicates that solvent ethanol also participated in the reaction as a substrate and this product 8 could be used in the preparation of acid hydrazide 3 according to Scheme 7. Taking this into account, a plausible mechanism was drawn for the formation of semicarbazones in the Scheme 7.…”

Section: Syn Thesismentioning

confidence: 99%

“…Interestingly, the problem has been solved in this work by protecting the terminal hydrazine moiety of acid hydrazide with aryl isocyanates, which led to substituted semicarbazides bearing several active functional groups. Treatment of the substituted semicarbazides with aldehyde in acidic ethanol led to a substitution reaction in which the semicarbazones and (3,5-di-tert-butyl-4-hydroxybenzylsulfanyl)acetic acid ethyl ester (8) are generated in greater yields than those obtained with existing methods.…”

Section: Paper Syn Thesismentioning

confidence: 99%

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Acid Hydrazide: A Potential Reagent for the Synthesis of Semicarbazones

Nath

Yehye

2018

Synthesis

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Complex semicarbazone derivatives were successfully synthesized from substituted semicarbazides in acidic ethanol upon heating in the presence of aldehyde. The reaction is functional group tolerant and chemoselective because no terminal hydrazine moiety is present in the substituted semicarbazides. Thus, functional groups such as esters and acetyls, which are prone to reaction with hydrazine, can also be used in this reaction because the terminal hydrazine moiety of the acid hydrazide was protected by aryl isocyanates in order to prepare substituted semicarbazides. In addition, neither of the aryl groups of semicarbazone are dependent on the starting materials (acid hydrazide) and can be changed upon demand. Thus, this reaction protocol provides a simple and effective alternative for the preparation of a wide variety of semicarbazones that could not be synthesized by utilizing conventional methods.

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Section: Syn Thesismentioning

confidence: 99%

Section: Syn Thesismentioning

confidence: 99%

Section: Syn Thesismentioning

confidence: 99%

Section: Paper Syn Thesismentioning

confidence: 99%

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Acid Hydrazide: A Potential Reagent for the Synthesis of Semicarbazones

Nath

Yehye

2018

Synthesis

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The Krapcho Dealkoxycarbonylation Reaction of Esters with α‐Electron‐Withdrawing Substituents

Krapcho

Ciganek

2013

Organic Reactions

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The Krapcho reaction involves esters with α‐electron‐withdrawing substituents such as malonates, β‐keto esters, and α‐cyano esters, which undergo dealkoxycarbonylation on being heated in polar aprotic solvents (such as DMSO, DMF, or HMPT) in the presence of water, or in polar aprotic solvents with water in the presence of added salts (such as NaCN, NaCl, LiCl, LiI, or MgCl 2 ). This procedure avoids the use of strongly aqueous acidic and alkaline conditions and tolerates many functional and protecting groups. The chapter presents the mechanistic aspects of this procedure, which include reaction parameters such as solvents, salts, other additives, and the use of microwave irradiation. The diastereoselectivity of protonation of the enolate intermediate leading to the dealkoxycarbonylated products is discussed. Trapping of the intermediate enolate by electrophiles other than a proton is illustrated. Potential side reactions and same‐pot subsequent reactions of substrates are discussed along with functional‐group compatibility for halogens and nitrogen, oxygen, sulfur, selenium, and carbon functional groups. Several examples of applications of this methodology for the synthesis of natural products along with experimental conditions and procedures are presented. Closely related methods are discussed in the Comparison with Other Methods section. The tables, which consist of 371 pages, are grouped according to substrate structure. Selective entries for other methods (excluding classical aqueous acidic or basic methods) are included in the tabular survey for comparative purposes.

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deesterification

Noir¹

2020

Catalysis From a to Z

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Chemoselective Addition of Hydrazine to δ‐Keto Esters and Dimethylformamide‐Mediated Deesterification

Cited by 4 publications

References 2 publications

Acid Hydrazide: A Potential Reagent for the Synthesis of Semicarbazones

Acid Hydrazide: A Potential Reagent for the Synthesis of Semicarbazones

The Krapcho Dealkoxycarbonylation Reaction of Esters with α‐Electron‐Withdrawing Substituents

deesterification

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