Orientation specific Diels–Alder addition of isoprene to an activated 4,4-dimethylcyclohexenone. An improved route to himachalenes

Liu, Hsing‐Jang; Browne, E. N. C.; Chew, S. Y.

doi:10.1139/v88-371

Cited by 21 publications

(18 citation statements)

References 5 publications

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“…These particular Lewis acids were chosen because we had previously observed that they were suitable as catalysts for related dienophiles (14,38,55,56). However, it was found that in the present case these Lewis acids gave poor to moderate yields of DielsAlder adducts (Table 1).…”

Section: Introductionmentioning

confidence: 83%

“…Our group (14,(35)(36)(37)(38) has carried out an intensive study of the Diels-Alder reactions of the 4,4-dimethyl-2-cyclohexen-1-ones 1-4. These studies have shown that structural features in the dienophile, such as the presence of a cross-conjugated carbalkoxy group or additional double bond, and the nature of the Lewis acid strongly influence the regioand stereoselectivity of the reaction.…”

Section: Introductionmentioning

confidence: 99%

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Facial selective Diels–Alder reactions of (1R,5R)-(+)-3-carbomethoxy-6,6-dimethylbicyclo[3.1.1]hept-3-en2-one. Unusual ketalization–fragmentation reaction of adducts

Liu¹,

Chew²,

Browne³

et al. 1994

Can. J. Chem.

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The stereofacially differentiated enone ester 5 has been used to study the effects of steric influence on the Diels-Alder reaction. In general, under Lewis acid catalysis, 5 adds to dienes at low to ambient temperatures in a reasonable rate. Yields of predictable chiral adducts are moderate with the unexpected exception of zinc chloride catalyzed reactions, which provide good to high yields. In all cases only products of addition to the Si face of general type 21 were observed. The regiochemistry of the adducts is exclusively that predicted by the ortho and para rules. The stereochemistry shows a high selectivity in favor of ester-endo transition state products. Rationales for the observed stereoselectivities are discussed. The fragmentation of adducts of 5, in particular keto ester 9, has been briefly examined. Olefins 30 and 46 derived from 9 have been converted to ring-opened cadinane skeletons 31 and 47, respectively, by conditions we have previously reported. In an entirely new and unexpected reaction, simultaneous ketalization and fragmentation of the cyclobutane ring of ketones derived from 9 gave ring-opened ketals 34 + 35 (from 29), 36 + 37 (from 9), 39 (from 38) and 42 + 43 (from 40).HSING-JANG LIU, SEW YEU CHEW, ERIC N.C. BROWNE et JEUNG BEA KIM. Can. J. Chem. 72, 1193Chem. 72, (1994.On a utilisC 1'Cnone ester 5 stCrCofacialement diffCrenciC pour Ctudier les effets stCriques sur la rCaction de Diels-Alder. En gCnCral, dans des conditions de catalyse acide de Lewis, le composC 5 s'additionne aux dibnes a des vitesses raisonnables, des tempkratures ne dCpassant pas la tempkrature ambiante. Les rendements des adduits chiraux attendus sont modCrCs, a l'exception notable des rkactions catalysCes par le chlorure de zinc qui donnent des rendements allant de bons 5 excellents. Dans tous les cas, on n'observe que les produits d'addition sur la face Si, de type gCnCral21. La rtgiochimie des produits est exclusivement celle que l'on peut prCdire sur la base des rbgles ortho etpara. La stCrCochimie prksente une grande sClectivitC pour les produits formCs par le biais de 1'Ctat de transition endo de l'ester. On a examink bribvement la fragmentation des adduits du produit 5, en particulier le cCto ester 9. Utilisant des conditions rapportCes antkrieurement, on a transform6 les olkfines 30 et 46, provenant du produit 9, en squelettes des cadinanes 2 cycle ouvert 31 et 47 respectivement. Par une rCaction aussi nouvelle qu'inattendue, une cktalisation et une fragmentation simultanCe du noyau cyclobutane des cCtones dCrivCs du produit 9 ont fourni les cCtals a cycles ouverts 34 + 35 (ii partir de 29), 36 + 37 (ii partir de 9), 39 (a partir de 38) et 42 + 43 (a partir de 40).[Traduit par la RCdaction]

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Section: Introductionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Facial selective Diels–Alder reactions of (1R,5R)-(+)-3-carbomethoxy-6,6-dimethylbicyclo[3.1.1]hept-3-en2-one. Unusual ketalization–fragmentation reaction of adducts

Liu¹,

Chew²,

Browne³

et al. 1994

Can. J. Chem.

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“…The installation of a triflate followed by Stille coupling afforded diene 12 in 72 % yield over two steps on a 10 g scale. Even though the intermolecular Diels–Alder reaction of enone–aldehyde 11 has been predicted to proceed via an endo transition state with regard to the aldehyde, and 11 would preferentially approach diene 12 from the side opposite to that occupied by the cyclopropane ring, the level of regioselectivity was uncertain in this scenario. Therefore, we were delighted to find the desired transformation proceeded smoothly in the presence of BF 3 ⋅OEt 2 (2.0 equiv) at −30 °C to afford 14 in 90 % yield; 1.3 equivalents of 12 were used to ensure the complete conversion of 11 .…”

Section: Figurementioning

confidence: 99%

Total Synthesis of Maoecrystal P: Application of a Strained Bicyclic Synthon

Kong

et al. 2017

Angew Chem Int Ed

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A new strategy was devised for the total synthesis of highly oxidized ent-kauranoids. A highly regio- and diastereoselective intermolecular Diels-Alder cycloaddition involving a diene embedded in a substituted bicyclo[4.1.0] skeleton was used to assemble all carbon centers but C17 of the target molecule at an early stage of the synthesis. Subsequent synthetic steps, including redox manipulations, SmI -mediated cyclization, and isomerization reactions, afforded the antitumor natural product maoecrystal P.

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“…Spectral data was consistent with that previously reported. 43 Methyl 5,5-Dimethyl-2-oxocyclohexanecarboxylate (6). Following the procedure used to prepare 2, 5 (9.6 g, 76 mmol) was treated with NaH (60% in oil, 12.2 g, 305 mmol), Me 2 CO 3 (16.0 mL, 190 mmol), and KH (30% in oil, catalytic amount) and then quenched with aq 3 M AcOH (120 mL) and poured into brine (100 mL).…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Bis-Michael Acceptors as Novel Probes to Study the Keap1/Nrf2/ARE Pathway

et al. 2016

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Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator that promotes the transcription of cytoprotective genes in response to oxidative/electrophilic stress. Various Michael-type compounds were designed and synthesized, and their potency to activate the Keap1/Nrf2/ARE pathway was evaluated. Compounds bearing two Michael-type acceptors proved to be the most active. Tether length and rigidity between the acceptors was crucial. This study will help to understand how this feature disrupts the interaction between Keap1 and Nrf2.

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Orientation specific Diels–Alder addition of isoprene to an activated 4,4-dimethylcyclohexenone. An improved route to himachalenes

Cited by 21 publications

References 5 publications

Facial selective Diels–Alder reactions of (1R,5R)-(+)-3-carbomethoxy-6,6-dimethylbicyclo[3.1.1]hept-3-en2-one. Unusual ketalization–fragmentation reaction of adducts

Facial selective Diels–Alder reactions of (1R,5R)-(+)-3-carbomethoxy-6,6-dimethylbicyclo[3.1.1]hept-3-en2-one. Unusual ketalization–fragmentation reaction of adducts

Total Synthesis of Maoecrystal P: Application of a Strained Bicyclic Synthon

Bis-Michael Acceptors as Novel Probes to Study the Keap1/Nrf2/ARE Pathway

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