Cyclizations of terminally substituted a,c-biladiene salts to give meso-substituted porphyrins

Smith, Kevin M.; Pandey, Ravindra K.

doi:10.1039/p19870001229

Cited by 6 publications

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“…The key starting materials, 2-formyl-5-iodopyrroles 4a − e are very easy to generate in three steps from the corresponding 2-methylpyrrole in high yields (as shown in Scheme ), involving (1) regioselective oxidation of the α-methyl group of pyrrole 5 using ceric ammonium nitrate to give pyrrole 6 ; (2) catalytic debenzylation of the esters using Pd−C in THF under H 2 to give pyrrole 7 , and (3) direct iodination to generate pyrrole 4 . An alternative method was used to prepare pyrrole 6c from 5c 17g through a Vilsmeier reaction (92% yield) as shown in Scheme .…”

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Improved Synthesis of Functionalized 2,2‘-Bipyrroles

et al. 2007

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A series of 2,2'-bipyrroles has been efficiently synthesized using an improved synthetic approach based on Pd(0)-catalyzed homocoupling of various 2-iodopyrroles. This new synthetic approach takes place at room temperature and in the presence of water. Functional groups such as formyl, ester, and nitrile are able to survive these reaction conditions. Solvents are found to play an important role in this reaction.

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Improved Synthesis of Functionalized 2,2‘-Bipyrroles

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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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ChemInform Abstract: Cyclizations of Terminally Substituted a,c‐Biladiene Salts to Give meso‐Substituted Porphyrins.

Pandey

1987

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Cyclizations of terminally substituted a,c-biladiene salts to give meso-substituted porphyrins

Cited by 6 publications

References 3 publications

Improved Synthesis of Functionalized 2,2‘-Bipyrroles

Improved Synthesis of Functionalized 2,2‘-Bipyrroles

TheVilsmeier Reaction of Fully Conjugated Carbocycles and Heterocycles

ChemInform Abstract: Cyclizations of Terminally Substituted a,c‐Biladiene Salts to Give meso‐Substituted Porphyrins.

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