Cationic molecular rearrangements of natural terpene compounds in superacidic media: reality and predictions

Barkhash, V. A.; Половинка, М. П.

doi:10.1070/rc1999v068n05abeh000469

Cited by 8 publications

(3 citation statements)

References 37 publications

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“…Barkhash and Polovinka 794 have reported in a series of papers the results of their extensive studies of the transformations of a large number of terpenoids induced by homogeneous and heterogeneous acids including fluorosulfuric acid. 2,3-Epoxygeraniol 208 was shown previously by Whittaker and co-workers 824 to afford epimeric oxabicyclooctanes in HSO 3 FÀSO 2 at 70 C [Eq.…”

Section: ð5:297þmentioning

confidence: 99%

Superacid‐Catalyzed Reactions

Oláh¹,

Prakash²,

Molnár³

et al. 2008

Superacid Chemistry

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Section: ð5:297þmentioning

confidence: 99%

Superacid‐Catalyzed Reactions

Oláh¹,

Prakash²,

Molnár³

et al. 2008

Superacid Chemistry

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“…The reviews that are published from time to time 13,14 just state the facts rather than analyse them, therefore they generally do not consider or discuss the mechanisms of the transformations described. The most recent reviews dealing with the rearrangements of terpenoids 3,15,16 give almost no consideration of the transformations of compounds with the carane skeleton.…”

Section: Introductionmentioning

confidence: 99%

Skeletal rearrangements of monoterpenoids of the carane series

Chuiko¹,

Vyglazov²

2003

Russ. Chem. Rev.

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Data on rearrangements of monoterpenoids with the Data on rearrangements of monoterpenoids with the bicyclo[4.1.0]heptane skeleton occurring by ionic, radical and bicyclo[4.1.0]heptane skeleton occurring by ionic, radical and concerted mechanisms are generalised and analysed. The biblio-concerted mechanisms are generalised and analysed. The bibliography includes 135 references graphy includes 135 references. .

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“…Studies of acid-catalyzed reactions of diepoxides derived from terpenoids in a wide range of acid media should provide information on the effect of the acidity of the medium on the direction of cationoid rearrangements, and comparison of the results with analogous data for transformations of initial dienes and their monoepoxy derivatives should elucidate how the mode of formation of cationic center is related to structure of the final products [9]. Studies in this field are also important from the synthetic viewpoint, taking into account that diepoxy derivatives of terpenoids are obtained from accessible and renewable starting materials and that new transformation products possessing oxygen-containing functional groups may be expected to exhibit biological activity.…”

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confidence: 99%

Transformations of caryophyllene diepoxides in various acidic media

et al. 2004

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Transformations of diepoxy derivatives of caryophyllene, a widely spread natural sesquiterpene, were studied in various acidic media under conditions of both homogeneous and heterogeneous catalysis. A number of previously unknown compounds were isolated. The experimental data were compared with the results of computer simulation of the most probable transformation pathways using molecular-mechanics and quantum-chemical methods.In the modern literature, little attention is given to the synthesis of diepoxy derivatives of terpenoids and their reactions in the presence of acid catalysts [1-6]; presumably, the reason is high reactivity of these compounds and their strong ability to undergo polymerization [6][7][8]. Studies of acid-catalyzed reactions of diepoxides derived from terpenoids in a wide range of acid media should provide information on the effect of the acidity of the medium on the direction of cationoid rearrangements, and comparison of the results with analogous data for transformations of initial dienes and their monoepoxy derivatives should elucidate how the mode of formation of cationic center is related to structure of the final products [9]. Studies in this field are also important from the synthetic viewpoint, taking into account that diepoxy derivatives of terpenoids are obtained from accessible and renewable starting materials and that new transformation products possessing oxygen-containing functional groups may be expected to exhibit biological activity.Caryophyllene (I) occupies a specific place among sesquiterpenoids due to diversity of its transformations. Acid-catalyzed reactions of caryophyllene give rise to compounds having clovane, caryolane, neoclovane, panasensane, and other skeletons [10][11][12][13].Treatment of diene I with peroxy acids leads to formation of epimeric epoxy derivatives as a result of oxidation of the endocyclic double bond: 4β,5α-epoxycaryophyllene (II) and its 4α,5β-isomer [13]. It should be noted that compound II is one of the most widely spread natural epoxides, and its transformations have been well documented [13,14]. Compound II can be isolated fairly readily (by crystallization) from a mixture of monoepoxy derivatives; repeated epoxidation gives a mixture of diastereoisomeric diepoxides IIIa and IIIb [15] (Scheme 1); transformations of the latter both over solid acid catalysts and in liquid acidic media have been reported.We calculated the most stable conformations of diepoxy derivatives IIIa and IIIb, which coincided with the previously described αα and βα conformations of caryophyllene [16,17]. The conformations were analyzed using Dreiding's models and molecular dynamics, and their stabilities were estimated by the molecular-mechanics method. The heats of formation of conformers were calculated in terms of the PM3 semiempirical approximation, and the most stable conformers (within 5 kcal/mol) were analyzed by the DFT method (B3LYP/6-31G*). Scheme 1 shows the best conformers (within 2 kcal/mol) according to the DFT calculations: the βα configuration of the 8...

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Cationic molecular rearrangements of natural terpene compounds in superacidic media: reality and predictions

Cited by 8 publications

References 37 publications

Superacid‐Catalyzed Reactions

Superacid‐Catalyzed Reactions

Skeletal rearrangements of monoterpenoids of the carane series

Transformations of caryophyllene diepoxides in various acidic media

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