Studier av 2-cykloaminoindener speciellt med hänsyn till prototropa omlagringar

• This thesis is a short review of six papers (Papers 1-6,page 5) concerning studies of enamines from 2-indanones. The unusually stable 2-(N-pyrrolidyl)indene has been studied (Paper 2 ). As a base catalyst this enamine rearranges 1-methylindene to 3-methylindene with a lower rate constant compared with triethylamine. During this 1, 3-prototropic rearrangement no hydrogen exchange was observed (Paper 1).Special attention has been drawn to 1,3-rearrangements ofalkyl-substituted enamines of 2-indanone. From 1-methyl-2-indanone, which was most conveniently prepared by oxidation of the corresponding indene, a series of enamines has been prepared with varying amine components. A study of the kinetic control of the formation of these enamines showed that the less substituted double-bond isomer was formed more rapidly than the other form. Furthermore, the nature of the amine group has a significant influence on the composition of the equilibrium mixture observed, but the isomeric ratios obtained were unexpected in the light of earlier investigations of enamines from 2-methylcyclohexanone (Paper l).A 13C NMR study of these 2-cycloaminoindenes showed that introduction of a 1-methyl substituent caused a decrease in overlap but the magnitude of this perturbation was almost independent of the variation of the amine component. Furthermore, when using pyrrolidineor hexamethyleneimine as amine parts this decrease in overlap was of a comparable magnitude with the diminished conjugation noted in the 3-methyl isomers. However, when piperidine or morpholine was used the decreased delocalization was more pronounced in the 3-methyl tautomers compared with the 1-methyl analogues (Paper6).One isomer, 1-methyl-2-(N-piperidyl)indene, has been shown to undergo base- as well as acid-catalyzed 1,3-tautomerizations in pyridine solvent. The isomerization rates using 1,4-diazabicyclo-(2.2.2.)octane or quinuclidine as base catalysts were considerably slower than the rate of the acid-catalyzed reaction or the base-catalyzed rearrangement rates involving alkyl-substituted indenes as substrates. This retarding effect, caused by the amine group, is in agreement with differences in pKA values obtained via simple Hückel calculation (Paper 4).The reaction between pyrrolidine and 1-(2-indanylidene)indan--2-one has been investigated. Two possible mechanisms were suggested for the formation of products consisting of a linear dienamine and an indenyl-substituted enamine (9:1). In the main product, isolated by recrystallization, the indenyl substituent was shown to be twisted out of conjugation. This dienamine also underwent acid-catalyzed isomerization to form the enamine product (Paper 3).Convenient syntheses of the pharmacologically interesting N-substituted 2-aminoindanes have also been described. The perchlorate salts of the enamines were treated with sodium borohydride in methanol to afford the desired products (Paper 5).

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NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

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