Azaindolizines. 2. Nitrogen N-5 and carbon C-1 and C-3 protonation of 1,3-disubstituted 5-azaindolizines

Fraser, M.

doi:10.1021/jo00984a026

Cited by 11 publications

(5 citation statements)

References 5 publications

(12 reference statements)

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“…6-Methyl-2-phenyl-5-azacycl[3.2.2]azine (20) was synthesized according to Boekelheide's procedure.2 2.6-Dimethyl-5-azacycl[3.2.2]azine (22). 2,7-Dimethyl-6-azaindolizine (2, 1.00 g) in nitrobenzene19 (20 ml) was added to dimethyl acetylenedicarboxylate (3 g) in nitrobenzene (20 ml).…”

Section: Methodsmentioning

confidence: 99%

“…The 1H NMR spectrum of one was consistent with it being 1 -formyl-5,7-dimethyl-2-phenyl-6azaindolizine (13) showing a considerable peri shift of the H-8 proton ( 8.04) with respect to the H-8 proton ( 6.88) of the parent 6-azaindolizine (4). The other aldehyde has been shown to be 4-formyl-6-methyl-2-phenyl-5-azacycl[3.2.2]azine ( 19), since the 6-methyl-2-phenyl-5-azacycl[3.2.2]azine (20), synthesized by Boekelheide's 1,3-dipolar addition procedure,2 gave on formylation approximately equal yields of the 1-and 4-formyl derivatives 23 and 1,9. The interpretation of the NMR spectra of these cyclazines is shown in Table III.…”

Section: Table Iiamentioning

confidence: 99%

“…b Chemical Shifts ( ) in the 100-MHz NMR Spectra of 5-Azacycl[3.2.2]azines[19][20][21][22][23][24] in CDC13 footnote a, TableI. b H-3 and H-4 values are tentative and arNe quoted in parentheses.…”

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confidence: 99%

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Azaindolizines. 3. Formylation studies on 6-azaindolizines

Buchan¹,

Fraser²,

Shand³

1976

J. Org. Chem.

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Section: Methodsmentioning

confidence: 99%

Section: Table Iiamentioning

confidence: 99%

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Azaindolizines. 3. Formylation studies on 6-azaindolizines

Buchan¹,

Fraser²,

Shand³

1976

J. Org. Chem.

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“…25 Protonation with trifluoroacetic acid leads to a mixture containing a species protonated at carbon atoms C-7 and C-7' (32%, 106a) and one at C-2 and C-7' (32%, 106b). Scheme 52 6-Aryl-pyrrolopyridazines were heteroarylated with yields in the range of 4-93% in the 7 position using as arylation agent 3,6-dichloropyridazines in dichloromethane as medium and in the presence of aluminium chloride (Scheme 53).…”

Section: Scheme 50mentioning

confidence: 99%

“…The synthesis of the intermediate pyrrolopyridazines 109 was performed using the Chichibabin reaction. 24,25,137 Usually the protonation of a N-aromatic heterocycle occurs at the nitrogen atom, but protonation at a ring carbon atom is also possible. From the studies performed on indolizine and its derivatives, it was shown that protonation occurs at position 3 or 1.…”

Section: Scheme 50mentioning

confidence: 99%

Pyrrolo[1,2-b]pyridazines. A revisit

Dumitraşcu¹,

Dumitrescu²

2008

Arkivoc

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TheVilsmeier Reaction of Fully Conjugated Carbocycles and Heterocycles

Jones

Stanforth

1996

Organic Reactions

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In 1925 Fischer, Müller, and Vilsmeier published a paper describing the reaction between phosphoryl chloride and N ‐methylacetanilide, giving a number of products, including the quinolinium salt and another salt. The probable course of the reaction was given in a paper by Vilsmeier and Haack in 1927, and they made the important discovery that the reagent obtained from N ‐methylformanilide and phosphoryl chloride, represented as a salt, would react with N,N ‐dimethylaniline, giving 4‐ N,N ‐dimethylaminobenzaldehyde. No 2‐substituted products were observed in this reaction. Other N,N ‐dialkylaniline derivatives, including 3, N,N ‐trimethylaniline and 1‐ N,N ‐dimethylaminonaphthalene were also successfully used as substrates to prepare aromatic aldehyde derivatives. The gradual development of the reagent for synthesis was accompanied by interest in the nature of the reagent. It was discovered that other acid chlorides (e.g., thionyl chloride, carbonyl chloride, and oxalyl chloride) could be used in the reaction and that substituted amides other than formamides gave ketones, although in generally poorer yields. Thionyl chloride frequently gives sulfur‐containing products. The most commonly used amide is dimethylformamide (DMF) and there is now a consensus that the reagent formed from DMF and most acid chlorides, other than phosphoryl chloride, can be represented by the structure given in the chapter, and this is illustrated for the reaction between DMF and carbonyl chloride. The salt is a stable compound and is often isolated before being reacted with a substrate. It seems likely that the most commonly used reagent, that made from DMF and phosphoryl chloride, is an equilibrium mixture of iminium salts. Recent unpublished spectroscopic studies have indicated that in DMF solution there is an equilibrium mixture of iminium compounds. One of the electrophilic chloroiminium salts then reacts with a substrate in an electrophilic substitution process yielding an iminium salt, which is usually hydrolyzed to the aromatic aldehyde. Vinylogous chloroiminium salts can be prepared from the corresponding vinylogous formamide derivatives and these yield, after hydrolysis, α,β‐unsaturated products. This particular reaction is generally limited to more reactive substrates. The formation of carbon–carbon bonds to fully conjugated carbocycles and heterocycles is the subject of this chapter; a subsequent chapter considers carbon–carbon bond‐formation reactions in alkenes (including heterosubstituted alkenes such as enamines and enol ethers), alkynes, and activated methyl and methylene compounds (aldehydes, ketones, carboxylic acid derivatives, and nitriles). It is not surprising that the Vilsmeier reaction has been the subject of many review articles of varying scope and length. With so many excellent reviews dealing with the Vilsmeier reaction, its mechanism, and the structure of the various electrophilic reagents, coverage is restricted to important concepts rather than reiterate all the literature material. A brief description of the mechanism and regiochemistry of the Vilsmeier reaction is presented and this is elaborated with appropriate cases that deal with specific compound types.

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Azaindolizines. 2. Nitrogen N-5 and carbon C-1 and C-3 protonation of 1,3-disubstituted 5-azaindolizines

Cited by 11 publications

References 5 publications

Azaindolizines. 3. Formylation studies on 6-azaindolizines

Azaindolizines. 3. Formylation studies on 6-azaindolizines

Pyrrolo[1,2-b]pyridazines. A revisit

TheVilsmeier Reaction of Fully Conjugated Carbocycles and Heterocycles

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