Synthesis of tetrahydrokhusitone: Annulation of the cyclohexane ring by free radical and carbanionic sequence of reactions

Petrović, Goran; Čeković, Živorad

doi:10.2298/jsc0305313p

Cited by 3 publications

(13 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The chemical shifts (d) are expressed in ppm using TMS as the internal standard. 13 C NMR spectra were measured on the same instrument at 50 MHz. Mass spectra were performed on a Finningan ITDS 700 instrument.…”

Section: Methodsmentioning

confidence: 99%

“…1 Hz, J 2 = 4.4 Hz, 1 H), 7.10-7.40 (m, 5 H). 13 C NMR (50 MHz): d = 141.3, 128.5, 126.6, 125.4, 87.0, 48.6, 40.9, 34.1, 31.5, 25.1, 22.9, 22.0, 20.9, 15.6. Elemental analysis was not performed because the compound decomposes with explosion in the Pregl apparatus (determined by 1 H NMR spectrum).…”

Section: Methodsmentioning

confidence: 99%

“…2.45 (s, 3 H), 4.00 (t, J = 6.4 Hz, 2 H), 7.57 (AA¢BB¢ system, d A = 7.36, d B = 7.79, J AB = 8.4 Hz, J AB¢ = 1.6 Hz, 4 H). 13 C NMR (CDCl 3 , 50 MHz): d = 209.3, 144.7, 133.0, 129.8, 127.8, 71.2, 38.6, 37.1, 34.8, 31.8, 29.9, 26.5, 23.6, 21.5 -1600, 1715, 1599, 1456, 1413, 1360, 1307, 1292, 1211, 1189, 1177, 1098, 958, 920, 816, 665 cm -1 . 1 1, 144.6, 133.1, 129.8, 127.8, 70.8, 40.7, 36.2, 32.6, 29.8, 28.9, 28.5, 26.9, 25.9, 22.9, 21.5, 13.9. Anal.…”

Section: 5-dimethyl-8-p-toluenesulfonyloxyoctan-2-one (From Hydroxymentioning

confidence: 99%

“…1 H NMR (200 MHz): d = 0.87 (d, J = 6.6 Hz, 3 H), 0.90 (d,J = 7.0 Hz,3 H),14 H),2.14 (s,3 H),2.42 (t,J = 7.0 Hz,2 H), 4.08 (br s, 1 H). 13 C NMR (50 MHz): d = 209.7, 67.8, 45.7, 45.7, 44.0, 43.9, 42.6, 35.0, 33.8, 33.7, 33.5, 33.2, 29.8, 29.6, 25.9, 24.1, 23.8, 22.3, 20.8, 20.7, 17.2, 16.8.…”

Section: Epimerization Of (1s2r4r)-hydroxy Ketone 31 Into (1s2s4rmentioning

confidence: 99%

“…In the reaction with methyl vinyl ketone the methyl group in position 9 was alkylated and hydroxy ketone 31 was obtained (the ratio of 6R and 6S is 1:3.5) which was then converted into the corresponding keto-tosylate. 13 The enolate anion 31a (Scheme 7) derived from the keto-tosylate, possessing an equatorial leaving group, did not undergo a substitution reaction, but rather an elimination reaction to give the unsaturated ketones 32. No traces of the cycloalkylation product 33 was obtained (Scheme 5).…”

mentioning

confidence: 99%

See 4 more Smart Citations

[4+2] Cyclohexane Ring Formation by a Tandem of a Free Radical Alkylation of a Non-Activated δ-Carbon Atom and Intramolecular Carbanion Cycloalkylation

Petrović¹,

Čeković²

2004

Synthesis

View full text Add to dashboard Cite

A [4+2] cyclohexane ring formation was achieved by the combination of free radical and ionic reaction sequences. Free radical alkylation of the remote non-activated d-carbon atom involves addition of d-carbon radicals, generated by 1,5-hydrogen transfer in alkoxyl radical intermediates, to the radicophilic olefins, while the polar sequence involves the enolate anions as intermediates which undergo a cycloalkylation reaction. The cyclohexane rings were constructed using diverse acyclic compounds 15 and 18 as well as cyclic alkyl arenesulfenates (e.g., 5, 24, 27) as the precursors of alkoxyl radicals (four-carbon atom fragment) and methyl vinyl ketone or other activated olefins as two-carbon atom fragments. Annulation of the cyclohexane ring was applied for the synthesis of a variety of cyclic systems including monocyclic (17 and 20), fusedrings (e.g. 23, 26, 29) and spirocyclic systems (7).Reactions and methods for carbocyclic ring construction are of great importance in organic synthesis. A variety of cyclization reactions were developed, which may involve cationic, radical and anionic intermediates, in addition to pericyclic and metal-catalyzed reactions. 1 In addition to the numerous classical reactions we recently discovered a new sequence of free radical and carbanionic reactions for the [4+2] annulation of cyclohexane ring 1, involving a carbon-carbon bond formation on the remote non-activated carbon atom (Scheme 1, step 2). 2 This cyclohexane ring annulation methodology is based on the recently discovered reaction of the d-carbon radical 3, generated by 1,5-hydrogen transfer in the alkoxyl radical intermediates (Scheme 1, step 1). It undergoes intermolecular addition to activated olefins and thus a functionalized alkyl chain was introduced at a remote non-activated carbon atom (Scheme 1, phase 2). 3,4 In these sequential free radical reactions the hydroxy compounds, possessing an electron-withdrawing group attached to the 6-position, are obtained. Compounds 2, possessing a suitably disposed procarbanionic carbon atom and leaving group offer the possibility for cyclohexane ring 1 closure (Scheme 1, step 3). 5 This method for the construction of a cyclohexane rings requires [4+2] carbon fragments and could be complementary to the Robinson annulation. 6 The four-carbon atom fragment must be a precursor of the alkoxyl radical generated from the alkyl arenesulfenates 4, while the two-carbon atom fragment is preferably an electron-deficient olefinic compound.The cyclohexane ring annulation methodology was verified using various structurally different four-carbon atom fragments as precursors of alkoxyl radicals. 3a Cycloalkylation reactions were applied to the synthesis of a variety of cyclic compounds including monocyclic, fusedring and spirocyclic systems (Scheme 2, Table 1). The alkyl arenesulfenates, used as precursors of the alkoxyl radicals, were part of acyclic, monocyclic and polycyclic systems and methyl vinyl ketone was used as an activated (radicophilic) olefin.The method for [4+2] cyclohexane ring annu...

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: 5-dimethyl-8-p-toluenesulfonyloxyoctan-2-one (From Hydroxymentioning

confidence: 99%

Section: Epimerization Of (1s2r4r)-hydroxy Ketone 31 Into (1s2s4rmentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

[4+2] Cyclohexane Ring Formation by a Tandem of a Free Radical Alkylation of a Non-Activated δ-Carbon Atom and Intramolecular Carbanion Cycloalkylation

Petrović¹,

Čeković²

2004

Synthesis

View full text Add to dashboard Cite

show abstract

Heteroatom-Centred Radicals for the Synthesis of Heterocyclic Compounds

Dénès

2018

Topics in Heterocyclic Chemistry

View full text Add to dashboard Cite

Natural sesquiterpenoids

Fraga

2004

Nat. Prod. Rep.

View full text Add to dashboard Cite

show abstract

Synthesis of tetrahydrokhusitone: Annulation of the cyclohexane ring by free radical and carbanionic sequence of reactions

Cited by 3 publications

References 10 publications

[4+2] Cyclohexane Ring Formation by a Tandem of a Free Radical Alkylation of a Non-Activated δ-Carbon Atom and Intramolecular Carbanion Cycloalkylation

[4+2] Cyclohexane Ring Formation by a Tandem of a Free Radical Alkylation of a Non-Activated δ-Carbon Atom and Intramolecular Carbanion Cycloalkylation

Heteroatom-Centred Radicals for the Synthesis of Heterocyclic Compounds

Natural sesquiterpenoids

Contact Info

Product

Resources

About

Synthesis of tetrahydrokhusitone: Annulation of the cyclohexane ring by free radical and carbanionic sequence of reactions

Cited by 3 publications

References 10 publications

[4+2] Cyclohexane Ring Formation by a Tandem of a Free Radical Alkylation of a Non-Activated δ-Carbon Atom and Intramolecular Carbanion Cyclo­alkylation

[4+2] Cyclohexane Ring Formation by a Tandem of a Free Radical Alkylation of a Non-Activated δ-Carbon Atom and Intramolecular Carbanion Cyclo­alkylation

Heteroatom-Centred Radicals for the Synthesis of Heterocyclic Compounds

Natural sesquiterpenoids

Contact Info

Product

Resources

About

[4+2] Cyclohexane Ring Formation by a Tandem of a Free Radical Alkylation of a Non-Activated δ-Carbon Atom and Intramolecular Carbanion Cycloalkylation

[4+2] Cyclohexane Ring Formation by a Tandem of a Free Radical Alkylation of a Non-Activated δ-Carbon Atom and Intramolecular Carbanion Cycloalkylation