1 1,2-dimethylcy

Dimedone derivatives. Dimedone or 6 6-dimethylci/cZohexane-1 3 dioiie j- in saturated aqueous solution J or in 10 per cent. alcohoUc solution gives crystalline derivatives (I) with aldehydes, but not with ketones. The reaction is ... 

Make molecular models of c/s and trans 1 2 dimethylcy clopropane and compare their strain energies... 

In competition, the less substituted alkenes displace more highly substituted alkenes (this can be virtually 100%, for example, 2,3-dimethylcy-clohexene versus 1,2-dimethyl cyclohexene.)... 

This method for the preparation of exo/ewdo-7-norcaranol is an adaptation of that described by Schollkopf, Paust, Al-Azrak, and Schumacher. The method has been used by the submitters for the preparation of the following cyclopropanols exo/endo-6-hydroxybicyclo[3.1. OJhexane, exo/e do-8-hydroxybicyclo[5.1.0] octane, exo/cwdo-9-hydroxybicyclo[6.1.0]nonane, 2,2-dimethylcy-clopropanol, 2,2,3,3-tetramethylcyclopropanol,Im 5-2,3-dimethyl cyclopropanol, cw-2,3-dimethyl-cf5//ran5-cyclopropanol, cis/ [Pg.45]

The relative configuration of cyclopropanes with attached nitrogen substituents can be determined by 15N chemical shifts. In the three stereoisomers of N-(l-ethoxy-2,3-dimethylcy-clopropyl)acetamide, the <5(I5N) value decreases by 5 to 7 ppm with the presence of each y-vi fl-oriented methyl group433 434. 

Problem 9.3 Indicate the geometric isomers, if any, for (n) 1,1,2-trimethylcyclopropane, (ft) 1,3-dimethylcy-clobutane, (c) 1,2,3-trimethylcyclohexane, (d) 1,2,4-trimethylcyclopentane, (e) I-methyl-2-propenylcyclopen-tane, (/) 2-chlorobicyclo(2.2.1 (heptane (common name is 2-chloronorbornane). 

Problem 9.16 (a) Draw the possible chair conformational structures for the following pairs of dimethylcy-dohexanes (i) cis- and trans-1,2-, (ii) cis- and frans-1,3- (iii) cis- and trans-lA-. (b) Compare the stabilities of he more stable conformers for each pair of geometric isomers, (c) Determine which of the isomers of limethylcyclohexane are chiral. <... 

The choice of catalyst is important, for instance the use of tetrakis(triphenylphos-phane)palladium(O) complex results in the quantitative cyclotrimerization of 3,3-dimethylcy-elopropene.17 In similar fashion 3,3-dimethoxycyclopropene cyciodimerizes to 3 (R = OMe, 74%) using bis(dibenzylideneacetone)paUadium(0) [Pd(dba)2] complex.18 The trisubstituted cyclopropene 4 is transformed to the head-to-head dimer 5 in the presence of copper(I) iodide.19... 

Oxaspiropentanes substituted in the cyclopropane part rearrange with preferential migration of the more substituted carbon atom. This is exemplified by the lithium iodide induced rearrangement of 4,4-dimethyl-l-oxaspiropentane which predominantly yielded 3,3-dimethylcy-clobutanone (3).44... 

Cyclopentane-1,3-diones 3 and 4 were prepared via a silver cation induced solvolysis of 2-bro-momethyl-2-hydroxycyclobutanones. This procedure represents a simple pathway to many 4-substituted and 4,5-disubstituled cyclopentane-1,3-diones.33 In particular, the reaction of 2-bromomethyl-2-hydroxy-3,3-dimethylcyclobutanone with silver nitrate gave 4,4-dimethylcy-clopentane-1,3-dione (3a) in 72% yield.33... 

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