A photochemical route to the formation of threo aldols

Schreiber, Stuart L.; Hoveyda, Amir H.; Wu, Hsien‐Jen

doi:10.1021/ja00341a077

Cited by 61 publications

(13 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[23][24][25] A succinimide as a C 4 building block would allow the sequential attachment of both the furan moiety (i.e., the second C 4 unit, required to construct ring D) and a 4,4dimethylpentane-2-one chain (precursor for ring B) to the same carbon atom in an arylation/Michael-addition sequence. [23][24][25] A succinimide as a C 4 building block would allow the sequential attachment of both the furan moiety (i.e., the second C 4 unit, required to construct ring D) and a 4,4dimethylpentane-2-one chain (precursor for ring B) to the same carbon atom in an arylation/Michael-addition sequence.…”

Section: Resultsmentioning

confidence: 99%

“…The precursor 22 for the [2 + 2] photocycloaddition was readily synthesized in six steps by starting from commercial 2methyl-1,3-cyclopentanedione (23), which was treated with dimethyl sulfate to afford methyl enol ether 24. Reaction with dimethyl malonate led to enone 25 and reduction with lithium aluminium hydride provided diol 26.…”

Section: Resultsmentioning

confidence: 99%

“…The photochemical key step in the third approach is an intramolecular Paternò-Büchi reaction of a ketone and a furan in precursor 32 to produce the tetracyclic system 31 (Scheme 7). [23][24][25] A succinimide as a C 4 building block would allow the sequential attachment of both the furan moiety (i.e., the second C 4 unit, required to construct ring D) and a 4,4dimethylpentane-2-one chain (precursor for ring B) to the same carbon atom in an arylation/Michael-addition sequence. The photoprecursor 32 was prepared by starting from maleimide 33.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Photochemical Approaches to the Bilobalide Core

Emsermann

Opatz

2017

Eur J Org Chem

View full text Add to dashboard Cite

Bilobalide is a tetracyclic sesquiterpene containing three contiguous γ‐lactone rings and an unusual tert‐butyl group, which is found in the leaves of the ginkgo tree (Ginkgo biloba). Three different photochemical approaches towards bilobalide's unique skeleton are presented. A meta photocycloaddition, a [2 + 2] photocycloaddition, and a Paternò–Büchi‐reaction were chosen as the respective key steps.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Photochemical Approaches to the Bilobalide Core

Emsermann

Opatz

2017

Eur J Org Chem

View full text Add to dashboard Cite

show abstract

“…This report has shown that only head‐to‐head product was produced with high exo face selectivity. Subsequently, this reaction was systematically explored by many groups, owing largely to the many pathways in which the 2,7‐dioxabicyclo[3.2.0]hept‐3‐ene ring system can be exploited (Scheme ).…”

Section: Photochemical‐assisted Synthesis Of Three‐membered and Four‐mentioning

confidence: 99%

Synthesis of Three‐Membered and Four‐Membered Heterocycles with the Assistance of Photochemical Reactions

Kaur

2019

Journal of Heterocyclic Chem

View full text Add to dashboard Cite

in Wiley Online Library (wileyonlinelibrary.com).Some transformations are not possible with ground-state reactions even in the presence of a catalyst; hence, they are performed under photochemical conditions. Electron transfer occurred even with the photochemical excitement of one molecule where redox reaction is not possible at the ground state. The side products were obtained from ground-state reactions. For C─C bond formation during photochemical reactions, there was no requirement of any chemical activation of the substrates. Therefore, these reactions are presented here for the synthesis of three-membered and four-membered heterocycles in the context of sustainable processes.

show abstract

“…Aliphatic aldehydes react with slightly lower exo-selectivity and a weak spin-selectivity effect (3) was determined; singlets favor the formation of the exo-diastereoisomer less pronounced than the corresponding triplets (4). 2 These photocycloadditions have been extensively used for synthetic applications especially because of the extraordinarily high degree of diastereocontrol (5)(6)(7)(8)(9)(10)(11)(12). Several other five-membered aromatic heterocycles were used as alkene components in the Paternò-Büchi photocycloaddition (13)(14)(15)(16)(17)(18)(19) and recently the oxazole-based route to α-amino β-hydroxy ketones was added by us (20).…”

Section: Introductionmentioning

confidence: 99%

Photo aldol reactions with 5-methoxyoxazoles: Highly regio- and diastereoselective synthesis of α-amino β-hydroxy carboxylic acid derivatives

Griesbeck¹,

Bondock²

2003

Can. J. Chem.

View full text Add to dashboard Cite

A versatile route to derivatives of α-amino β-hydroxy carboxylic acids, either with tertiary (from a corresponding glycine equivalent) or a quaternary α-carbon center is described. The key reaction is the cycloaddition of electronically excited carbonyl compounds (aromatic and aliphatic aldehydes, respectively) to oxazoles. To make the products hydrolytically more labile, a methoxy substituent at position C-5 was introduced leading to the formation of cycloadducts with an orthoester substructure. The photocycloaddition, either with triplet excited (aromatic) carbonyls or with singlet excited (aliphatic) carbonyls, led to the formation of mixtures of endo-and exo-diastereoisomers with moderate to very high exo-selectivities. The 4-unsubstituted 5-methoxyoxazole 1 (glycine equivalent) gave the [2 + 2]-adducts 3a-3f with aldehydes 2a-2f in high yields and excellent diastereoselectivities. Hydrolysis of these compounds resulted in the α-amino β-hydroxy esters 4a-4f with preferred erythro (S*,S*) configuration. As an extension of this process, 4-alkylated 5-methoxyoxazoles 5a-5f were applied as alkene components and the corresponding cycloadducts with benzaldehyde 6a-6f were obtained. Again, the exo-diastereoisomers were formed as the major products in diastereoselectivities from 73:27 (exo:endo) up to >95:5. Hydrolysis of these adducts resulted in the formation of α-amino β-hydroxy esters 7a-7f with like (S*,S*) configuration of the major diastereoisomers.Résumé : On décrit une voie versatile pour obtenir des acides α-amino-β-hydroxycarboxyliques portant des centres α-carbonés tertiaire (à partir de la glycine équivalente correspondante) ou quaternaire. La réaction clé est une cycloaddition de composés carbonylés électroniquement excités (aldéhydes aromatiques et aliphatiques respectivement) à des oxazoles. Afin de que les produits soient plus facilement hydrolysables, on a introduit un substituant méthoxyle en position C-5 afin d'obtenir des cycloadduits comportant une structure orthoester. La photocycloaddition, avec des carbonyles (aromatiques) excités à l'état triplet ou avec des carbonyles (aliphatiques) excités à l'état singulet, conduit à la formation de mélanges de diastéréomères endo-et exo-dans lesquels la sélectivité en faveur de l'exo-est de modérée à très élevée. La réaction du 5-méthoxyoxazole non substitué en position 4 (1) (équivalent de la glycine) avec les aldéhy-des 2a-2f donne les adduits [2 + 2] 3a-3f avec des rendements élevés et d'excellentes diastéréosélectivités. L'hydrolyse de ces composés conduit aux α-amino-β-hydroxyesters 4a-4f avec la configuration érythro (S*,S*) pré-férée. Comme extension de ce procédé, on a utilisé les 5-méthoxyoxazoles alkylées en position 4 (5a-5f) comme composants alcéniques et, par réaction avec les benzaldéhyde, on a obtenu les cycloadduits correspondants 6a-6f. Une fois de plus, les diastéréoisomères se forment comme produits majeurs, avec des diastéréosélectivités allant de 73:27 (exo:endo) jusqu'à >95:5. L'hydrolyse de ces produits conduit à la formation des α...

show abstract

A photochemical route to the formation of threo aldols

Cited by 61 publications

References 7 publications

Photochemical Approaches to the Bilobalide Core

Photochemical Approaches to the Bilobalide Core

Synthesis of Three‐Membered and Four‐Membered Heterocycles with the Assistance of Photochemical Reactions

Photo aldol reactions with 5-methoxyoxazoles: Highly regio- and diastereoselective synthesis of α-amino β-hydroxy carboxylic acid derivatives

Contact Info

Product

Resources

About