Applications of NMR Spectroscopy in Organic Chemistry.

4.04 – Pyrazoles and their Benzo Derivatives

Synthesis and reactivity of 2-(carboxymethyl)aziridine derivatives.

Ring opening of donor–acceptor cyclopropanes with various N-nucleophiles provides a simple approach to 1,3-functionalized compounds that are useful building blocks in organic synthesis, especially in assembling various N-heterocycles, including natural products In this review, ring-opening reactions of donor–acceptor cyclopropanes with amines, amides, hydrazines, N-heterocycles, nitriles, and the azide ion are summarized 1 	Introduction 2 		Ring Opening with Amines 3 	Ring Opening with Amines Accompanied by Secondary Processes Involving the N-Center 31 	Reactions of Cyclopropane-1,1-diesters with Primary and Secondary Amines 311 	Synthesis of γ-Lactams 312 	Synthesis of Pyrroloisoxazolidines and -pyrazolidines 313 	Synthesis of Piperidines 314 	Synthesis of Azetidine and Quinoline Derivatives 32 	Reactions of Ketocyclopropanes with Primary Amines: Synthesis of Pyrrole Derivatives 33 	Reactions of Сyclopropane-1,1-dicarbonitriles with Primary Amines: Synthesis of Pyrrole Derivatives 4 	Ring Opening with Tertiary Aliphatic Amines 5 	Ring Opening with Amides 6 	Ring Opening with Hydrazines 7 	Ring Opening with N-Heteroaromatic Compounds 71 	Ring Opening with Pyridines 72 	Ring Opening with Indoles 73 	Ring Opening with Di- and Triazoles 74 	Ring Opening with Pyrimidines 8 	Ring Opening with Nitriles (Ritter Reaction) 9 	Ring Opening with the Azide Ion 10 	Summary

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Ring Opening of Donor–Acceptor Cyclopropanes with N-Nucleo­philes

Enaminones in heterocyclic synthesis

The reactions of ethyl 3-ethoxymethylene-2, 4-dioxovalerate (1a) and ethyl ethoxy-methyleneoxaloacetate (1b) with indole analogs (2, 14, 17-19) are described. Treatment of 1a, b with 2 in ethanol followed by refluxing in acetic anhydride afforded 3, 4, 10-trisubstituted pyrimido [1, 2-a] indoles (4a, b). Hydrogenation or nucleophilic addition of 4a, b was found to occur on the pyrimidine ring in a 1, 4-fashion. Compounds 1a, b were also reacted with 14 in ethanol under ice cooling to give the 3, 4-disubstituted 9H-pyrimido-[2, 3-b] indoles (15a, b) directly. Indole (17) or 2-methylindole (18) reacted with 1a (or 1b) to give a mixture of 3-indolylmethylene derivatives (20a, b and 21a, b) and tris-(3-indolyl)-methanes (23 and 24).

Reactions of Ethyl 3-Ethoxymethylene-2,4-dioxovalerate and Ethyl Ethoxymethyleneoxaloacetate with Indole Analogs

Reaction of ethyl 3-ethoxymethylene-2,4-dioxovalerate and ethyl ethoxymethyleneoxaloacetate with 3-aminopyrazole analogs. Synthesis and chemistry of 3,6,7-trisubstituted pyrazolo[1,5-a]pyrimidine derivatives

Synthesis and reactions of ethyl 3-acetyl-8-cyano-6,7-dimethylpyrrolo[1,2-a]pyrimidine-4-carboxylate and related compounds

The pyrolysis of benzyl 2-oxazolecarbamates (I) and benzyl 4-alkylallophanates (II) was investigated. Heating of benzyl 5-phenyl-2-oxazolecarbamate (Ia) at 230°C gave benzyl alcohol and 2-phenyl-6-(5-phenyl-2-oxazolyl)-5H-oxazolo [3, 2-α] [1, 3, 5] triazine-5, 7-(6H)-dione (IIIa). Compound IIIa was also obtained by heating the azide prepared from 5-phenyl-2-oxazolecarbohydrazide (IVa). In the same way, 2-methyl-6-(5-methyl-2-oxazolyl)-5H-oxazolo [3, 2-α] [1, 3, 5] triazine-5, 7 (6H)-dione (IIIb) and 2-phenyl-6-(5-phenyl-2-thiazolyl)-5H-thiazolo [3, 2-α] [1, 3, 5] triazine-5, 7 (6H)-dione (IIIc) were obtained from the corresponding hydrazides (IVb and IVc). Next, heating of benzyl 4-(2-phenylethyl)-allophanate (IIa) at 230°C gave cyanuric acid (VII), benzyl (2-phenylethyl) carbamate (VIII) and 1, 3-bis (2-phenylethyl)-1, 3, 5-triazine-2, 4, 6 (1H, 3H, 5H)-trione (IX).

Pyrolysis of Benzyl 2-Oxazolecarbamates and Benzyl 4-Alkylallophanates

Durch Kondensation des Aminoimidazols (II) mit den Ethoxymethylenverbindungen (I) werden die Imidazopyrimidine (IV) hergestellt, deren Umsetzung mit Diazomethan (VI) untersucht wird.

Keiko Nasu

Papers

Reactions of Ethyl 3-Ethoxymethylene-2,4-dioxovalerate and Ethyl Ethoxymethyleneoxaloacetate with Indole Analogs

Reaction of ethyl 3-ethoxymethylene-2,4-dioxovalerate and ethyl ethoxymethyleneoxaloacetate with 3-aminopyrazole analogs. Synthesis and chemistry of 3,6,7-trisubstituted pyrazolo[1,5-a]pyrimidine derivatives

Synthesis and reactions of ethyl 3-acetyl-8-cyano-6,7-dimethylpyrrolo[1,2-a]pyrimidine-4-carboxylate and related compounds

Pyrolysis of Benzyl 2-Oxazolecarbamates and Benzyl 4-Alkylallophanates

Synthesis and reactions of ethyl 6-acetyl-2,3-diphenylimidazo(1,2-a) pyrimidine-5-carboxylate and related compounds.