Selektive Funktionalisierung von Polyenen

The reductive cleavage of methyl vinyl-β-ionyl ether (1) or the deprotonation of 3,2Ј,6Ј,6Ј-tetramethyl-5-(1-cyclohexenyl)-1,3-pentadiene (2) gives rise to an organometallic C 15 species that combines selectively with a variety of electrophiles at the terminal chain position. Its reaction with aldehydes, however, is less clean. In particular, (E)-β-formyl-2-butenyl acetate gives the expected adduct 7a and, after dehydration, vitamin A acetate only in poor yield. The same is true for the analogous reaction with 2,7-dimethyl-2,4,6-octa-3-Methoxy-3-methyl-1-(2,6,6-trimethyl-1-cyclohexenyl)-1,4-pentadiene (1), quantitatively obtained by the treatment of vinyl-β-ionol with sodium hydride and methyl iodide in tetrahydrofuran or with dimethyl sulfate in the presence of sodium hydroxide under phase-transfer conditions, is readily cleaved by lithium metal or sodium/potassium alloy. The resulting heptatrienyl-type organometallic C 15 entity [1Ϫ3] can be trapped by standard electrophiles to afford, for example, the hydrocarbon 3, the silane 4 or the alcohol 5. As we have found more recently, the same C 15 species can be generated conveniently by the deprotonation of 3-methyl-5-(2,6,6-trimethyl-1-cyclohexenyl)-1,3-pentadiene (2) with sec-butyllithium or the superbasic mixture of butyllithium and potassium tert-butoxide. The required triene is easily prepared by a Wittig olefination of (E)-2-methyl-4-(2,6,6-trimethyl-1-cyclohexenyl)-2-butenal, [4Ϫ5] the key building block in the Isler/Hoffmann-LaRoche syntheses of vitamin A [5Ϫ7] and β-carotene. [7Ϫ8] (E)-3-Formyl-2-butenyl acetate is, along with vinyl-β-ionol, the major component of the Pommer/BASF route [9Ϫ10] to vitamin A. When this aldehyde was allowed to react with the organometallic C 15 species, regardless of [a] 3903 triendial, which ultimately affords β-carotene. Vitamin A acetate can also be prepared, this time in moderate yield, by functionalization through consecutive deprotonation, borylation, oxidation and acetylation of a C 20 pentaene hydrocarbon having the required skeleton. Both the C 15 and the C 20 organometallic key intermediates adopt spontaneously a zigzag-like outstretched conformation which, upon electrophilic trapping, directly and exclusively leads to the all-(E) configuration.

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“…Distillation gave a colorless liquid; bp 90Ϫ92°C/ 1 Torr (ref. : [32] bp 60Ϫ62°C/0.1 Torr); n 20 D ϭ 1.5141; yield 44.0 g (87%). …”

Section: 33-trimethyl-2-[(2e)-3-methyl-24-pentadienyl]cyclohexenementioning

confidence: 99%

The Organoalkali Route to Vitamin A and β-Carotene

2001

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“…The formed solid was collected by filtration, washed with ethanol, dried and crystallized from the proper solvent. 4,6, [3,2-e] [1,2,4]triazolo [3,4- General procedure for the preparation of 3c,d…”

Section: Generalmentioning

confidence: 99%

“…The solid so-precipitated was filtered off and crystallized from benzene. [3,2-e] [1,2,3,4]tetrazolo [1,5- General procedure for the preparation of 4`a,b…”

Section: 467-tetramethyl-45-dihydrothieno[32-e][124]triazolo[mentioning

confidence: 99%

“…The biological [1][2][3][4][5], bactericidal [6], and medicinal [7,8] activities of thieno [2,3-d]-pyrimidine derivatives have stimulated considerable research in this field [9][10][11][12]. In continuation of our work on the synthesis of fused pyrimidine derivatives [13], we report here the utility of 3-methyl-2-methylthio-3,4-dihydrotheino [2,3-d]pyrimidine-4-one derivatives 1a,b for the synthesis of azolothienopyrimid-ines, thienopyrimido-as-triazines, pyrazolylthienopyrimidines and tetrazolothienopyrimidines.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of Polynuclear Heterocyclic Compounds Derived from Thieno[2,3-d]pyrimidine Derivatives

El‐Gazzar

Hassan

2000

Molecules

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Abstract:Reaction of 2-hydrazino-3-methyl-3,4-dihydrothieno [2,3-d]pyrimidin-4-one derivatives 2a,b with aliphatic acids afforded the thienotriazolopyrimidinone derivatives 3a-d, with nitrous acid yielded tetrazolothienopyrimidinone derivatives 4a,b and with carbon disulphide furnished 3-mercaptothienotriazolopyrimidinone derivatives 5a,b. Also, 2a,b reacted with aldehydes to afford the arylhydrazones 6a-f which cyclized into thienotriazolopyrimidinone derivatives 7a-f. Furthermore, 2a,b condensed with ethyl acetoacetate and ethyl cyanoacetate to afford 2-(1-pyrazolyl) derivatives 9a,b and 10a,b, respectively. On the other hand, 2-hydrazino derivatives 2a,b condensed with α-halo-ketones to yield thienpyrimidotriazinone derivatives 11a,b and with β-diketones, to form 2-(1-pyrazolyl) derivatives 12a-f.

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“…It was found that functionalized thiadiazines have insecticidal [2], antibacterial [3], herbicidal [4], and fungicidal [5] effects. The broad biological activities of pyrimidine [6–12] and fused pyrimidine derivatives, prompted us to synthesize new derivative of pyrimidines fused heterocycles. During last decade, we were investigating the behavior of Mannich reaction toward the multifunctional heterocyclic compounds such as 5‐mercapto‐3‐aryl‐1,2,4‐triazole (Fig.…”

Section: Introductionmentioning

confidence: 99%

Intramolecular cyclization of Mannich reaction for synthesis of pyrimido[2,1‐b]‐1,3,5‐tiadiazines

El‐Sherief

Hozien

EL‐Mahdy

et al. 2010

Journal of Heterocyclic Chem

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in Wiley Online Library (wileyonlinelibrary.com).Reaction of 6-aryl-5-cyano-2-mercapto-3,4-dihydropyrimidin-4-ones with formaldehyde and primary amines in suitable solvent via a double Mannich reaction gave the corresponding 8-aryl-7-cyano-3-Nsubstituted-pyrimido[2,1-b]-1,3,5-thiadiazin-6-ones rather than the isomeric products 6-aryl-7-cyano-3-N-substituted-pyrimido[2,1-b]-1,3,5-thiadiazin-8-ones. The cyclization method was found to be the most favored for the formation of the linear products rather than the angular isomers. This was confirmed not only by using spectral analysis and molecular mechanical calculations but also by X-ray single crystal structure determination.

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Selektive Funktionalisierung von Polyenen

Cited by 26 publications

References 9 publications

The Organoalkali Route to Vitamin A and β-Carotene

The Organoalkali Route to Vitamin A and β-Carotene

Synthesis of Polynuclear Heterocyclic Compounds Derived from Thieno[2,3-d]pyrimidine Derivatives

Intramolecular cyclization of Mannich reaction for synthesis of pyrimido[2,1‐b]‐1,3,5‐tiadiazines

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