Skeletal rearrangements of monoterpenoids of the carane series

Chuiko, V. A.; Vyglazov, O. G.

doi:10.1070/rc2003v072n01abeh000735

Cited by 14 publications

(6 citation statements)

References 61 publications

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“…The non-conjugated epoxide (4) from (+)-3-carene (3) did not react in the same manner (Scheme 2) [6,7]. We have since found similar behaviour with the tosyl aziridines 5 and 6 (Scheme 3) [8][9][10].…”

Section: Introductionmentioning

confidence: 52%

“…Chuiko and coworkers have reported a Prins reaction of compound 1 in which the cyclopropane ring was not opened, indicating that the tertiary carbocation was formed rather than the cyclopropyl carbinyl cation (Scheme 1) [2]. As Chuiko has pointed out [3], this suggests strongly that the vinyl cyclopropane in compound 1 is not conjugated. Chuiko [3,4] and Brown [5] have also presented further evidence of a lack of conjugation in compound 1.…”

Section: Introductionmentioning

confidence: 88%

“…As Chuiko has pointed out [3], this suggests strongly that the vinyl cyclopropane in compound 1 is not conjugated. Chuiko [3,4] and Brown [5] have also presented further evidence of a lack of conjugation in compound 1.…”

Section: Introductionmentioning

confidence: 96%

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Reactions of the halonium ions of carenes and pinenes: An experimental and theoretical study

et al. 2015

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The reactions of vinylcyclopropane (+)-2-carene (1) and vinylcyclobutanes (-)-β-pinene (7), (-)-α-pinene (11), and (-)-nopol (12) with electrophilic halogens in the presence of oxygen and nitrogen nucleophiles in various solvents have been investigated. The halonium ion intermediates that were presumably formed were very reactive and led to opening of the conjugated cyclopropane or cyclobutane. Reactions of chloramine-T trihydrate with compound 1 in acetonitrile gave amidine 13 and diazepine 14. Reactions of chloramine-T trihydrate with pinenes in methylene chloride gave allylic tosylamines 22, 16B and 24. Mechanisms to explain the observations are proposed and supported by ab initio and Density Functional Theory calculations on the carenes and pinenes in this report and their bromonium ion intermediates. For comparisons, the relative extent of conjugation with the bromonium ion moiety of these, as well as select cyclohexene and cyclohexadiene systems and their corresponding bromonium ions, were optimized at the B3LYP/cc-pVDZ level of theory, and then these geometries were analyzed using the absolute hardness index at the HartreeFock/aug-cc-pVDZ and B3LYP/aug-cc-pVDZ levels of theory. Additionally, Natural Population Analysis charges were calculated for these systems using Møller-Plessett Second-Order Perturbation Theory electron densities and the aug-cc-pVDZ basis set. Combining the results of these theoretical methods with analysis of structural details of their optimized geometries gives much electronic structure insight into the extent of conjugation of bromonium ions of the carenes and pinenes reported here, and places them in relative context of more traditional conjugated and non-conjugated bromonium ion systems. In particular, bromonium ions of compounds 1, 7, and 11 display structural distortions, charge delocalizations and hardness values comparable with those of traditional conjugated cyclohexadienes, with possible reasons for subtle differences presented.

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Section: Introductionmentioning

confidence: 52%

Section: Introductionmentioning

confidence: 88%

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Reactions of the halonium ions of carenes and pinenes: An experimental and theoretical study

et al. 2015

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“…Although it contains a vinylcyclopropane [2,3], 1 has been shown that the two functions are non-conjugated [4][5][6], and they react accordingly, for example, giving products from a Prins reaction in which the cyclopropane remains intact [6].…”

Section: Introductionmentioning

confidence: 99%

Cyclopropyl aziridines: solvolytic reactions of the N-tosylaziridines of (+)-2-carene and (+)-3-carene

Silverberg

Rabb

Reno

et al. 2014

Heterocyclic Communications

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The N-tosylaziridine 4 of (+)-2-carene 1 was prepared and subjected to solvolytic reactions with weak protic acids. For comparison, the solvolytic reactions of cis-3-carene-N-tosylaziridine 8 were also studied. The solvolyses of 4 were more rapid than those of 8, and both rings were opened in 4, whereas only the aziridine was opened in 8. This leads to the conclusion that the aziridine and cyclopropane rings in 4 can achieve a conjugated transition state.

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“…The examples of formally probable pairs of valence tautomers of 1H-, 2H-, 3H-, and 4H-azepines with azanorcaradienes are shown on Scheme 2. The existence of valence tautomerism monocycle bicycle is reliably established for the substituted cycloheptatrienes and some of their heterocyclic analogs, for instance, oxepines [9,10,12,26,27], yet this type of concerted reactions is not investigated up till now. Still less data exist on the valence tautomerism of azacycloheptatrienes.…”

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confidence: 99%

Heterocumulenes reactions with organometallic reagents: XV. Quantum-chemical investigatiom of skeleton rearrangements of 2-methyl-6-methoxy-3H-azepine originating from valence tautomerism

et al. 2010

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In the framework of quantum-chemical simulation (DFT) the structure was explored of six potentially probable tautomeric forms of 2-methyl-6-methoxy-3H-azepine and their relative thermodynamic stability was evaluated. In the tautomers obtained the preferred gradient channels are localized of [1,n]-H shifts capable of initiating their tautomerism. The most probable typical concerted reactions were analyzed of the formation of valence isomers, fused three-/six-and four-/five-membered carbo-and heterocycles, azabicyclo[4.1.0]hepta-2,4-dienes (azanorcaradienes) and azabicyclo[3.2.0]hepta-3,6-dienes respectively. Azepines (azacycloheptatrienes) and their hydrogenated derivatives were recently described in many synthetic, theoretical, and medical publications [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], first of all owing to the biological activity of these substances [2][3][4]. Azepine derivatives find wide and versatile application in pharmacology, mainly as psychotropic, antidepressant and anticonvulsant drugs, and also as antiviral, antibacterial, and anticancer pharmaceuticals [4]. The azepine structures find also interesting applications in the organic synthesis [5]. Besides these heterocycles are convenient models for further investigation of aromaticity and antiaromaticity [6][7][8], for the study of valence tautomerism [8][9][10][11][12][13][14][15][16][17][18], sigmatropic rearrangements [16,17,19], various stereochemical problems (transannular effect of the unshared electron pair of the heteroatom, formation of intramolecular hydrogen bonds) [2,13,16,20], for quantum-chemical calculations [6, 11-13, 20, 21]. The heightened interest to the seven-membered azaheterocycles stimulates the search for and development of new and at the same time simpler, cheaper and more general procedures for their preparation, in particular, those that lead to new derivatives, for the range of available representatives of this class compounds is still narrow.Recently [22,23] we developed a fundamentally new general approach to the simultaneous building up of azepine and dihydroazepine cycles by a mild deprotonation of 2-aza-1,3,5-triene systems that in their turn easily formed from lithiated allenes or alkynes and isothiocyanates [24]. For instance, previously unknown and difficultly available by another route 2-methyl-6-methoxy-3H-azepine (Ia) and 7-methyl-2-(methyl-sulfanyl)-3-methoxy-4,5-dihydro-3H-azepine (II) were synthesized from α-lithiated methoxyallene, isopropyl isothiocyanate, and methyl iodide along Scheme 1 [23]. In the absence of the deprotonating base 1-aza-1,3,4-triene III and the product of its [1,5]-sigmatropic rearrangement, 2-aza-1,3,5-triene IV, undergo thermally induced intramolecular cyclization reactions with the formation of pyrrole V and 2,3-dihydropyridine VI [24].The azepine molecules (according to XRD and NMR data existing mainly in the boat conformation) are known [2] to be fairly labile that shows in slow stereochemical transformations, sigmatropic rearrangements with the ...

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Skeletal rearrangements of monoterpenoids of the carane series

Cited by 14 publications

References 61 publications

Reactions of the halonium ions of carenes and pinenes: An experimental and theoretical study

Reactions of the halonium ions of carenes and pinenes: An experimental and theoretical study

Cyclopropyl aziridines: solvolytic reactions of the N-tosylaziridines of (+)-2-carene and (+)-3-carene

Heterocumulenes reactions with organometallic reagents: XV. Quantum-chemical investigatiom of skeleton rearrangements of 2-methyl-6-methoxy-3H-azepine originating from valence tautomerism

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