Regiocontrolled synthesis of phenacylpyrroles

Abstract

A series of2,4-disubstituted phenacylpyrroles were synthesized from the reaction of 2-substituted vinamidinium salts with cx-aminoacetophenone hydrochloride. Reactions of a vinylogous amide, a chloropropeniminium salt and a f3-chloroenal with cx­ aminoacetophenone hydrochloride were carried out under acidic, neutral and basic conditions. The best conditions for making a 2,3,4-trisubstituted phenacylpyrrole are with the f3-chloroenal under basic conditions. The regioselectivity of the substrate under those three conditions was evaluated. By performing GC analysis and using the GC-MS selective ion technique, a minor isomer was detected and the products and ratios of g isomers were determined. The reiochemistry of the major isomer was determined by performing a NOEDIF experiment on the N-methylated pyrrole product. A series of f3- chloroenals with different substituents (methyl, butyl, phenyl, hydrogen) at the ex-position were produced and used under the best conditions to make a series of2,3,4-trisubstituted phenacylpyrroles. The resulting 3,4-diphenyl-2-phenacylpyrrole is a potential precursor to a Polycitone A analog. When the starting material is 3-chloro-2-butyl-3-phenyl-2- propenal, a small amount of2,3,5-trisubstituted phenacylpyrrole was isolated and characterized. Multistep reactions towards a "pyrrole first" synthesis ofbis-des-hydroxyrigidin were carried out using ethyl benzoyl acetate as the starting material. The first step was fonnation of a vinylogous amide followed by a reaction with cx-aminoacetophenone forming an amine exchanged product. Intramolecular cyclization gave the 2,3,4- trisubstituted pyrrole precursor. Electrophilic rons were conducted and brominated and nitrated products were obtained. Such compounds represent potential precursors to bis-deshydroxyrigidin.

Notes

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Graduation Date

1994

Semester

Fall

Advisor

Gupton, John T.

Degree

Master of Science (M.S.)

College

College of Arts and Sciences

Department

Chemistry

Format

PDF

Pages

184 p.

Language

English

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

Identifier

DP0028684

Subjects

Arts and Sciences -- Dissertations, Academic; Dissertations, Academic -- Arts and Sciences

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