Intramolecular Diels−Alder Reaction by Self-Assembly of the Components on a Lewis Acid Template

Ward, Dale E.; Abaee, M. Saeed

doi:10.1021/ol0067235

Cited by 69 publications

(38 citation statements)

References 52 publications

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“…This method involves with the existence of a free hydroxyl group in the diene and a carbonyl in the dienophile to coordinate all reagents and led to very good facial selectivities. 2,4-Pentadienol was combined with nitroso dienophiles, 12,13 and methyl acrylate 14,15 in the presence of tartaric acid or BINOL with excellent selectivities. We have previously reported on some control in reactions of diene 1a with maleimides.…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%

Asymmetric Diels–Alder cycloadditions of d-erythrose 1,3-butadienes to achiral t-butyl 2H-azirine 3-carboxylate

Duarte

Faustino

Alves

et al. 2013

Tetrahedron: Asymmetry

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Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%

Asymmetric Diels–Alder cycloadditions of d-erythrose 1,3-butadienes to achiral t-butyl 2H-azirine 3-carboxylate

Duarte

Faustino

Alves

et al. 2013

Tetrahedron: Asymmetry

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“…[13] This methodology afforded the cycloaddition adducts 7 and 9 from conjugated the 1,3-dienes 6 a and 8, respectively, as single regio-and diastereoisomers. [14] No conversions were detected in the absence of lutidine, and could indicate that a possible hydroxy-directed [15] mechanism is involved. This procedure constitutes a straightforward route to complex polycyclic systems with a controlled stereochemistry.…”

Section: Methodsmentioning

confidence: 99%

Metal‐Triflate‐Catalyzed Synthesis of Polycyclic Tertiary Alcohols by Cyclization of γ‐Allenic Ketones

2014

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It has been established that bismuth(III) triflate catalyzes the cyclization of g-allenic ketones under mild reaction conditions. This reaction allows the selective formation of polycyclic tertiary alcohols from cyclic ketone derivatives. The resulting dienols can engage in stereoselective cycloadditions to efficiently afford complex polycyclic systems.Complex polycyclic molecules have always fascinated organic chemists, and their rapid, reliable, and efficient synthesis constitutes a motivating challenge to accept. Cycloisomerization reactions are undoubtedly powerful and provide a sustainable means to generate molecular complexity with good control of selectivity.[1] In this context, the intramolecular carbonyl-ene reaction represents a very useful tool for the efficient formation of substituted cyclohexanols, [2] and has been widely used in natural product synthesis. Because of the relatively high energetic barrier, carbonyl-ene processes often require high temperatures or the employment of Lewis acids, usually in excess (Prins reaction). Despite its reliability, this reaction presents some important limitations, such as the difficulty in forming five-membered rings because of the higher cyclization energy requirement induced by geometric factors. In addition, ketones are intrinsically much poorer enophiles than aldehydes in these reactions. Cyclizations involving ketone derivatives have been reported [3] and include highly activated ketones such as trifluoromethylketones [4] or a-ketoesters.[5]The cyclization of carbonyl-allene compounds has been mainly studied under thermal, [6] radical, [7] and transitionmetal-catalyzed [8] processes. Herein we present our results concerning the metal-triflate-catalyzed cyclization of g-allenic ketones. We anticipated that allenes could be used as ene components to bias the geometric cyclization for the formation of five-membered rings. Moreover, the higher reactivity of allenes, as compared to alkenes, should allow the reaction with ketones to proceed under mild reaction conditions. We first used the acyclic b-ketoester 1 bearing a pendant trisubstituted allene as a model and assessed its reactivity towards various metal triflate catalysts in nitromethane (Table 1, entries 1-4). A rapid screening highlighted nonexpensive bismuth(III) triflate [9,10] as a very active catalyst at low loading with the total conversion of 1 occurring at À20 8C. Switching solvents from nitromethane to CH 2 Cl 2 considerably slowed down the reaction rate and led to the isolation of the cyclopentadienes 2 b and 2 c in good yield (88 %) at room temperature by using only 1 mol % of bismuth(III) triflate (entry 5). The formation of 2 b could arise from the elusive ene product 2 a undergoing an elimination reaction. Hydration of compound 2 b could lead to the tertiary alcohol 2 c.To prevent the elimination of the alcohol in 2 a, a reaction which is possibly favored by the position of OH group b to the ester, the reactivity of the allenic cyclohexanone derivative 3 was examined (Scheme 1)....

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“…The prototype of this reaction was originally reported by Ward and Abaee [150] in 2000, with a less satisfactory selectivity. Nicolaou and Harrison utilized a different ligand (27) and obtained the desired 28 as the only product in 80% yield.…”

Section: The Synthesis Of Abyssomicin Cmentioning

confidence: 99%

A new era for organic synthesis—highlights of the recent progress

Yikang

2007

Front. Chem. China

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The major progress in organic synthesis since 2005 is briefly surveyed in two parts. The first part deals with some of the most impressive advances in the synthetic methodology, which includes: (1) metal-mediated synthetic reactions, with an emphasis on the olefin metathesis and gold-mediated reactions; (2) free radical-based organic synthesis; (3) synthetic transformations performed in a "one-pot" manner involving either tandem reactions or multicomponent reactions; (4) asymmetric reactions catalyzed by metal and organo-catalysts. The major advances in total synthesis of some complex natural products with significant biological activities are presented in the second part, with detailed illustrations of ten selected molecules, including dragmacidin F, abyssomicin C, 11-acetoxy-4-deoxyasbestinin D, pentacycloanammoxic acid, UCS1025A, (−)-merrilactone A, nigellamine A 2 , (+)-saxitoxin, and Tamiflu (an artificially designed natural product-like molecule). An array of complicated structures of the natural products synthesized over the last two years is also listed to serve as a convenient lead to the original literature for the prospective interested readers.Keywords organic synthesis, metal-mediated synthetic reaction, free radical reaction, "in one pot" reaction, asymmetric reaction, total synthesis of natural products Organic reactions are of central importance to organic synthetic methodology and underlie all types of organic A new era for organic synthesis-highlights of the recent progress

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Intramolecular Diels−Alder Reaction by Self-Assembly of the Components on a Lewis Acid Template

Cited by 69 publications

References 52 publications

Asymmetric Diels–Alder cycloadditions of d-erythrose 1,3-butadienes to achiral t-butyl 2H-azirine 3-carboxylate

Asymmetric Diels–Alder cycloadditions of d-erythrose 1,3-butadienes to achiral t-butyl 2H-azirine 3-carboxylate

Metal‐Triflate‐Catalyzed Synthesis of Polycyclic Tertiary Alcohols by Cyclization of γ‐Allenic Ketones

A new era for organic synthesis—highlights of the recent progress

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