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Reference: D. F. Nisbet, (1971). The chemistry of adducts from acetylenes and quinaldines. DPhil. University of Oxford.Citable link to this page:

 

The chemistry of adducts from acetylenes and quinaldines

Abstract: ´╗┐This thesis is divided into two parts. The first partconcerns the chemistry of products obtained from substituted2-methylquinolines and dimethyl acetylenedicarboxylate,and the second part describes an attempted X-ray crystallographicstructure determination of one of these products,the structure of which could not be elucidated by chemicalmethods.In Part 1, Chapter 1, the previously known types ofreactions of nitrogen-containing heterocycles withacetylenecarboxylic acids and their esters are reviewed.The investigations reported here concern new reactionsbetween substituted 2-methylquinolines and dimethylacetylenedicarboxylate; also, some previously describedreactions were reinvestigated. These reactions usuallygave complex mixtures which were resolved chromatographicallyA number of separate types of product were formed, and thesetypes are considered in separate chapters.In Chapter 2 the benzo[c]quinolizines and azepinessuch as (1) and (2), and the isomeric azepine (3), obtainedfrom the reactions of substituted 2-methylquinolines withdimethyl acetylenedicarboxylate are discussed.The u.v., n.m.r., i.r. and mass spectra of these compoundsare entirely analogous to those of known benzo[c]quinolizinesand azepines. New azepines (4), (5) and (6) were obtainedfrom 2-ethylquinoline and (7) from 2-benzylquinoline;their structures were deduced from the u.v., n.m.r. andmass spectra.The isolation of these compounds with a methyl- or a phenyl-groupat position 10 or 11 has necessitated a re-appraisalof one mechanism of azepine-formation, and a new schemeinvolving a spiro intermediate is proposed (Scheme 1).The 4a-isopropyl-4aH-benzo[c]quinolizine (8) is thesole product of the reaction of 2-isopropylquinoline withdimethyl acetylenedicarboxylate; this undergoes a smoothphoto-isomerisation to the 1-isopropyl-1H-benzo[c]quinolizine(9).Chapter 3 discusses the red adducts formed in thereactions of 2-methyl-, 2,8-dimethyl- and 2,6,8-trimethylquinolinewith dimethyl acetylenedicarboxylate. Two redadducts are formed in each of these reactions, and it isproposed that these are geometric isomers of the structures(10), (11) and (12) respectively.The n.m.r. spectra of these compounds show the 6- and 7-protonsas AX quartets in the range 2.8andndash;3.5andtau;; the 11- and12-protons and the 17-protons appear as AX quartets andsinglets respectively in the range 4.4andndash;6.2andtau;. The chemicalshifts of the 11-, 12- and 17- protons permit a simpleclassification into two groups, first and second redadducts. Shielding of the 11-ester methyl groups of thefirst red adducts, but not of their isomers, by the benzo-ringcauses these methyl resonances to occur upfield fromthe other ester-methyl resonances. The n.m.r. spectra intrifluoroacetic acid solution are discussed. The red adductsreadily eliminate the elements of dimethyl fumarate (maleate)in the mass spectrometer.The first red adducts from 2-methyl- and 2,8-dimethylquinolineare most conveniently prepared pure by usingmethanol as the reaction solvent, as the first red, but notthe second red, adducts crystallise from the reaction mixture.Bromination of the first red adduct from 2-methylquinolinegives the quinoline (13), which is readily debrominated togive the quinoline (14). Compound (14) is also obtaineddirectly by treatment of the first red adduct from 2-methylquinolinewith zinc in glacial acetic acid. Formation ofcompounds (13) and (14) involves the elimination of fumarate(maleate) from the red-adduct molecules, as also occurs inthe mass spectrometer. This facile elimination, whenconsidered in conjunction with the shielding effects observedin the n.m.r. spectra, provides good evidence in favourof a red-adduct structure involving a saturated-CHE.CHE-groupingattached to the nitrogen atom.Hydrogenation of the first red adducts from 2-methyl-and 2,8-dimethyl-quinoline in glacial acetic acid solutionusing Adams' catalyst gives the hexahydro-derivatives (15)and (16) respectively; the tetrahydro-derivative (17) isobtained from the 2-methylquinoline adduct using 10%palladium-on-charcoal. The spectral properties of thederivatives (13)andndash;(17) are discussed.A mechanism to account for the formation of the redadducts is proposed. Alternative structures for the redadducts, and the reasons for rejecting them, are discussed.The surprising observation that the benzo[c]quinolizines,azepines and other adducts (Chapter 4) formed when these2-methylquinolines are reacted with dimethyl acetylenedicarboxylatein acetonitrile solution, are not formed whenmethanol is used as the reaction solvent, is noted.A red compound isolated in very low yield from thereaction of 2,4-dimethylquinoline with dimethyl acetylenedicarboxylatein methanol is assigned the structure (18) onspectral evidence.Chapter Four deals with other adducts isolated fromthe reactions of substituted 2-methylquinolines withdimethyl acetylenedicarboxylate. Analogues of the knownadduct (19) are obtained from 2,8-dimethyl-, 2,6,8-trimethyl-and 2,4,6,8-tetramethyl-quinoline (compounds (20)andndash;(22)respectively).An adduct assigned the structure (23) on the basis of then.m.r. and u.v. spectra is obtained in very low yield from2,4,6,8-tetramethylquinoline.The adduct (24) is also obtained from 2,4,6,8-tetramethylquinoline,although the alternative structure (25), andcorresponding structures for the degradation products,are not excluded. Catalytic reduction of this adductusing Adams' catalyst gives the phenols (26) and (27)by hydrogenolysis; the ether (28) is readily formed fromthe phenol (27) by methylation with ethereal diazomethane.Mixtures obtained by treating adduct (24) with both bromineand zinc in glacial acetic acid are discussed. Mechanismsaccounting for the formation of both structures (24) and (25)are presented; it is not possible to differentiate betweenthese structures on the basis of the present work.Yellow adducts isolated from the reactions of 2,8-dimethyl-,2,6,8-trimethyl- and 2,4,6,8-tetramethyl-quinolinewith dimethyl acetylenedicarboxylate are tentatively assignedthe structures (29)andndash;(31) respectively. A computer-simulatedn.m.r. spectrum is in good agreement with the observedAMX pattern of the -CH2-CHE- grouping of adduct (29) inthe range 5.4andndash;7.9andtau;. Irradiation of a methanolic solutionof the adduct (31) with ultra-violet light yields a photoisomer.Part 2, Chapter 5, concerns the blue adducts formedin the reactions of 2-methyl-, 2,8-dimethyl-, 2,6,8-trimethyl-and 2-ethyl-quinoline with dimethyl acetylenedicarboxylate,the latter two of which were first isolatedin the present investigation. The 2-methylquinoline blueadduct has a molecular weight of 679, corresponding to acomposition of 1 mole quinoline + 4 moles ester andminus; 1 molemethanol. Treatment of this adduct with bromine in glacialacetic acid yields a dark green isomer, but an attemptedreduction with zinc in glacial acetic acid gave only polymericester. As the information obtainable from these reactions,and from the spectral data of the blue adducts, was verylimited, an attempt was made to determine the structureof the 2-methylquinoline blue adduct by X-ray crystallography.This attempt failed, the most likely reason beingthat the total atomic contents of the unit cell were toogreat for the available computer programme to handle.The n.m.r., u.v. and mass spectra of the blue adductsare discussed. The n.m.r. spectra suggest that the 2-methyl-and 2,8-dimethyl-quinoline adducts may not be analogues;the mass spectrum of the latter suggests that the molecularweight could be 707, and not 693 as stated by Gagan.The extremely broad absorption bands in the visible spectraof the adducts appear to be charge-transfer bands.[For the figures to accompany this abstract, please consult the PDF]

Type of Award:DPhil Level of Award:Doctoral Awarding Institution: University of Oxford Notes:This thesis was digitised thanks to the generosity of Dr Leonard Polonsky

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Dr. R.M. AchesonMore by this contributor

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Dr. A.R. HandsMore by this contributor

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Issue Date: 1971Identifiers

Urn: uuid:fbfe9f72-6ada-4c97-ab53-d41510f6f5e2

Source identifier: 601870679 Item Description

Type: Thesis;

Language: eng Tiny URL: td:601870679

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Author: D. F. Nisbet - institutionUniversity of Oxford oxfordCollegeQueen's College, The - - - - Contributors Dr. R.M. Acheson More b

Source: https://ora.ox.ac.uk/objects/uuid:fbfe9f72-6ada-4c97-ab53-d41510f6f5e2



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