A Tether Controlled <i>e</i><i>xo</i>-Selective Trans-Annular Diels−Alder (TADA) Reaction

Felzmann, Wolfgang; Arion, Vladimir B.; Mieusset, Jean‐Luc; Mulzer, Johann

doi:10.1021/ol061510m

Cited by 25 publications

(10 citation statements)

References 19 publications

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“…Our strategy started with enamine reduction of anti ‐2 l with NaCNBH 3 under an acidic condition, and the subsequent treatment of the crude residue with m CPBA through Cope elimination to produce α,β‐unsaturated lactone 7 in 82 % yield over two steps. The stereoselective Michael addition of 7 was then performed with vinylmagnesium bromide in the presence of CuCl to afford the β‐vinyl substituted lactone 8 as a single diastereomer in 88 % yield . The essential cyclohexyl ring was constructed with Grubbs catalyst to form tricyclic lactone 9 in 92 %.…”

Section: Methodsmentioning

confidence: 99%

Tandem [1,2]‐Wittig Rearrangement/Lactonization of γ‐Benzyloxy Vinylogous Urethanes: Application to the Synthetic Studies of Maculalactone A, Planchol C and γ‐Lycorane

2017

Asian J Org Chem

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At andem [1,2]-Wittig rearrangement/lactonization of g-benzyloxy vinylogousu rethanes is presented herein. The resulting butenolides featuring various benzyl substituents at the g-position are structurally diverse compounds found in natural products. The usefulness of this synthetic approach was demonstrated in the formal synthesis of maculalactone A, rapid assemblyo ft he tricyclic core of planchol C, and the total synthesis of g-lycorane.The rearrangemento fa-alkoxyc arbanions is one of the important reaction for CÀCb ondf orming methods. In particular,t he [2,3]-Wittig rearrangement,w hich allow the transformationo f an allylic ether into ah omoallylic alcohol, has been highly developedi nv arious fields of organic synthesis.[1] By contrast, the [1,2]-Wittig rearrangement has received less attention [2] and has rarely been applied in the synthesis of naturalp roducts [3] and pharmaceuticals.[2s] This lack of popularity has mainly resulted from the preparation of a-etherealc arbanions, which relies heavily on the use of the benzyl group as ac arbanionstabilizing group in the anion formation step (Scheme 1a). However,t he stability and synthetic potentialo ft he phenyl ring limits the synthetic applications of this approach. [1,2]-shifts of electron-withdrawing group (EWG)-bearing ethers involvingt he formation of new stereocenters are scarce, because EWGs stabilizing the a-ethereal carbanions can sometimesu ndergo eliminationr eactions to form carbonyl compounds (Scheme 1b).[4] To date, only af ew examples have been reported that allow accesst ot he corresponding carbinols in the presenceo fE WGs, such as ketones, [5] acetamides, [6] and b-lactams (Scheme 1c).[7] Recently,s ignificant progress has been made using an asymmetric tandem [1,2]-Wittig/Aldol or [1,2]-Wittig/Mannich reactions of glycolate esters, which provide a,b-dihydroxy esters and a-hydroxy b-amino esters in high stereoselectivities, respectively. [3b, 8] These tandem approaches not only strikingly complement traditional carbanion-stabilizing groups but also allow ac ascade sequence to efficiently forge complex chemical structures.Inspired by our previouss tudies on the asymmetric aldol reaction of g-benzyloxy vinylogousu rethanew ith aldehydes, under certain circumstances, aminute amount of g-benzyl substitutedv inylogous urethane lactone was obtained (Scheme 2a). [9] We envisioned that the rearrangement of av inylogous urethane system possessing an EWG-bearing moiety and ab enzyloxy-migrating terminus might undergo at andem [a] Dr

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Section: Methodsmentioning

confidence: 99%

Tandem [1,2]‐Wittig Rearrangement/Lactonization of γ‐Benzyloxy Vinylogous Urethanes: Application to the Synthetic Studies of Maculalactone A, Planchol C and γ‐Lycorane

2017

Asian J Org Chem

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“…These interesting heterocyclic compounds are potentially useful building blocks for asymmetric synthesis, with THFs 14 structurally similar to catechol-O-methyl transferase (COMT) bisubstrate inhibitor 16 and the anti-tumour natural product (+)-varitriol 17. 27 Similarly, lactones 15 have been widely employed previously as building blocks for asymmetric synthesis directed towards natural products such as the antibiotic 18 (Scheme 7) 28 . Previously reported syntheses of these lactones are lengthy (6 steps) and required the use of harsh workup procedures and toxic solvents.…”

Section: Scheme 5 Selective Dehydration Of the Anti Sugar Thioacetalmentioning

confidence: 99%

“…Synthesis of chiral heterocycles from selected ketene dithioacetals via i) Lewis acid mediated reaction with electrophilic dimethyl acetal to give lactone 13 ii) borate ester B(OCH2CF3)3 mediated dehydration 26 to give THF 14, with structural similarity to the natural product (+)-varitriol, 27 iii) Lewis acid mediated dehydration to give lactone 15. Catechol-O-methyltransferase (COMT) bisubstrate inhibitor 29 , (+)-varitriol 27 and Branimycin intermediate 28 show with structurally similar glucose derived THF and arabinose-derived lactone scaffolds highlighted in red.…”

Section: Scheme 5 Selective Dehydration Of the Anti Sugar Thioacetals Via Initial Acetylation 21 Followed By Basemediated Eliminationmentioning

confidence: 99%

“…Similarly, lactones 15 have been widely employed previously as building blocks for asymmetric synthesis directed towards natural products such as the antibiotic 18 (Scheme 7) 28 . Previously reported syntheses of these lactones are lengthy (6 steps) and required the use of harsh workup procedures and toxic solvents.…”

Section: Scheme 5 Selective Dehydration Of the Anti Sugar Thioacetals Via Initial Acetylation 21 Followed By Basemediated Eliminationmentioning

confidence: 99%

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Regioselective Dehydration of Sugar Thioacetals under Mild Conditions

Szpara¹,

Goyder²,

Porter³

et al. 2020

Preprint

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Pentose and hexose sugars are abundant constituents of waste biomass, making them sustainable, chiral building blocks for organic synthesis. The demand for chiral saturated heterocyclic rings from the pharmaceutical industry is increasing as they provide well-defined three-dimensional frameworks that show increased metabolic resistance. Through the formation of thioacetals, sugars may be manipulated in their straight-chain form and dehydrated selectively under basic conditions at C-2. This approach was applied to an array of sugars and extended to the production of useful chiral THFs via further selective dehydration reactions.

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“…105 The hypervalent iodine-mediated oxidative dearomatization-Diels-Alder cascade was investigated as a means of preparing the [2.2.2]bicyclic core of the natural product tashironin. Trapping of allyl alcohols during the oxidative dearomatization of phenol (95) produced the desired five-membered acetal (96), whereas trapping of the allenyl alcohols resulted in the undesired six-membered acetal (97) (Scheme 25).…”

Section: + 4-cycloadditionmentioning

confidence: 99%

Addition Reactions: Cycloaddition

Dennis¹

2010

Organic Reaction Mechanisms · 2006

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A Tether Controlled exo-Selective Trans-Annular Diels−Alder (TADA) Reaction

Cited by 25 publications

References 19 publications

Tandem [1,2]‐Wittig Rearrangement/Lactonization of γ‐Benzyloxy Vinylogous Urethanes: Application to the Synthetic Studies of Maculalactone A, Planchol C and γ‐Lycorane

Tandem [1,2]‐Wittig Rearrangement/Lactonization of γ‐Benzyloxy Vinylogous Urethanes: Application to the Synthetic Studies of Maculalactone A, Planchol C and γ‐Lycorane

Regioselective Dehydration of Sugar Thioacetals under Mild Conditions

Addition Reactions: Cycloaddition

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