Transannular Diels–Alder cyclization of substituted 13-membered trienes. An approach to the B.C.D.[6.6.5] rings of the 14β-hydroxysteroids

1996 ◽  
Vol 74 (2) ◽  
pp. 129-143 ◽  
Author(s):  
Pascal Langlois ◽  
Pierre Soucy ◽  
Yves L. Dory ◽  
Pierre. Deslongchamps
Keyword(s):  
Key Words ◽  
Diels Alder ◽  
Enol Ether ◽  
Trans Diene

The transannular Diels–Alder strategy has been applied to three 13-membered macrocyclic trienes whose characteristics are: a cis-trans diene and a cis methoxymethyl enol ether as the diénophile. The successful trials led to three 6.6.5 tricyles having a trans-syn-cis geometry exactly as in the B.C.D. rings of the 14β-hydroxysteroids. Key words: transannular, Diels–Alder, 14β-hydroxysteroids, 13-membered rings.

scholarly journals Studies on the transannular Diels–Alder reaction of 15-membered macrocyclic trienes containing a trans-trans diene. Part I: Synthesis and isomerization of various model cyclopentadecatrienes

1995 ◽  
Vol 73 (10) ◽  
pp. 1675-1694 ◽  
Author(s):  
Dennis G. Hall ◽  
Renate Müller ◽  
Pierre Deslongchamps
Keyword(s):  
Aqueous Media ◽  
Alder Reaction ◽  
Membered Ring ◽  
Diels Alder ◽  
Coupling Reactions ◽  
Diels Alder Reaction ◽  
Trans Diene

The transannular Diels–Alder reaction of 15-membered macrocyclic trienes with a trans-trans-cis (TTC) olefin geometry can lead to A.B.C.[6.6.7] tricyclic products of trans-syn-trans (TST) and cis-syn-cis (CSC) stereochemistry whereas the TTT isomers can produce the trans-anti-cis (TAC) and cis-anti-trans (CAT) tricycles. In order to study the influence of the position (pro-6.6 or pro-6.7) and the nature (alkyl, alkoxymethyl, or formyl) of the dienophile substituent, a set of 10 model cyclopentadecatrienes was prepared. The synthesis of appropriately functionalized trisubstituted dienophile and diene synthons, as well as their coupling reactions affording acyclic precursors, is described in this paper (first in a series of two). A mild and efficient macrocyclization protocol yielded the required methyl- or alkoxymethyl-substituted cyclic substrates. Further transformations led to the formyl-substituted ones. In particular, the TTT macrocycles containing an enal as a dienophile could be completely isomerized to the corresponding TTC thermodynamic isomers in acidic aqueous media. Keywords: transannular, Diels–Alder, 15-membered ring, A.B.C.[6.6.7] tricycles, diterpene.

Acyl cyanides as carbonyl heterodienophiles: application to the synthesis of naphthols, isoquinolones, and isocoumarins

1996 ◽  
Vol 74 (2) ◽  
pp. 221-226 ◽  
Author(s):  
Richard Connors ◽  
Elisabeth Tran ◽  
Tony Durst
Keyword(s):  
Key Words ◽  
Diels Alder ◽  
Acetonitrile Solution ◽  
Carbon And Nitrogen ◽  
Nitrogen Nucleophiles ◽  
Derivatives Of

Irradiation of 2-methylbenzoyl cyanide (3a) in acetonitrile solution results in the formation of its dimer, which upon loss of HCN gives rise to the cycloadduct 7a. The dimerization also proceeds efficiently with derivatives of 3a giving adducts 7b and 7c. When 2-methylaroyl cyanides are photolyzed in the presence of a more reactive acyl cyanide the mixed adducts 8a–e are obtained in excellent yields. The cycloadducts 7a–c and 8a–e react with carbon and nitrogen nucleophiles by a tandem addition–cyclization sequence furnishing substituted naphthols (10a and 10b) and isoquinolones (11a–d), respectively. Isocoumarins 12a and 12b were prepared from the adducts 8a and 8e by treatment with potassium tert-butoxide in THF. Key words: naphthols, isoquinolones, isocoumarins, synthesis of; acyl cyanides; hetero Diels–Alder.

scholarly journals Cycloadditionen, XXI [1]. 2-Methyl-2,3-butadiensäure-arylester; Synthese und thermische Reaktivität / Cycloadditions, XXI [1] Aryl 2-methyl-2,3-butadienoates; Synthesis and Thermal Reactivity

1994 ◽  
Vol 49 (1) ◽  
pp. 63-75 ◽  
Author(s):  
Gerhard Himbert ◽  
Dieter Fink ◽  
Martina Stürm
Keyword(s):  
Acid Chloride ◽  
Catalytic Amount ◽  
Diels Alder ◽  
Alternative Route ◽  
Substituted Phenols ◽  
Enol Ether ◽  
Methyl Group ◽  
Thermal Reactivity ◽  
Tricyclic Ketone

Abstract The substituted phenyl, 1-naphthyl or the 9-anthrylmethyl esters of the 2-methyl-(or 2-phenyl)-2,3-alkadienoic acids (see 4 a -g , 9 a -d and 12a,b) are synthesized by condensation of the allenic acids 2 a -d with the substituted phenols 3 a -g , with 1-naphthol (8) or with 9-anthrylmethanol (11) in the presence of dicyclohexyl carbodiimide (DCC) and a catalytic amount of 4-dimethylaminopyridine (DMAP). An alternative route is the reaction of the acid chloride la with the phenols 3 a -c (see formation of 4 a -c) in the presence of triethylamine. All these compounds (except 12a) undergo the intramolecular Diels-Alder (IMDA)-reaction to form the tricycles 6 a -g , 10 a-d and 13. The enol ether 6a is hydrolized during chromatography to give the tricyclic ketone 7. The influence of the geminal methyl group on the rate of the IMDA-reaction is investigated. 9-Anthryl-and (2,4,6-cycloheptatrien-1-on-2-yl)-2-methyl-2,3-butadienoate (15, 17), formed by reaction of 2-methyl-2,3-butadienoyl chloride (1a) with 9-anthrone (14) and 2-tropolone (16) isomerise spontaneously to the IMDA-products 19 and 18.

Diels–Alder reactions of activated 2H-thiopyrans

1991 ◽  
Vol 69 (10) ◽  
pp. 1487-1497 ◽  
Author(s):  
Dale E. Ward ◽  
Yuanzhu Gai ◽  
Wajdi M. Zoghaib
Keyword(s):  
Thermal Decomposition ◽  
Key Words ◽  
Diels Alder ◽  
Reaction Conditions ◽  
Approximate Order

The Diels–Alder reactivity of various 2H-thiopyrans bearing electron-donating substituents has been investigated. The approximate order of reactivity among the 2H-thiopyrans studied was 4,6-disubstituted [Formula: see text] 5-substituted > 4-substituted, 3,5-disubstituted [Formula: see text] 3-substituted. Good yields of predominantly endo adducts are obtained with reactive dienophiles. With less reactive dienophiles, reactions are much slower and yields are attenuated due to the competing thermal decomposition of the dienes under the reaction conditions. The adducts obtained are equivalent (via desulfurization) to those from unreactive cis-substituted dienes. Key words: Diels–Alder, 2H-thiopyran.

Total synthesis of d,l-quassin

1991 ◽  
Vol 69 (5) ◽  
pp. 853-855 ◽  
Author(s):  
Nada Stojanac ◽  
Zdenek Valenta
Keyword(s):  
Total Synthesis ◽  
Key Words ◽  
Ammonium Hydroxide ◽  
Enol Ether ◽  
Key Steps

The completion of the total synthesis of d,l-quassin 1 is described. Key steps are a facile intramolecular acylation of a protected cyanohydrin carbanion (4 → 5), a selective deprotonation with trioctyl methyl ammonium hydroxide leading to the removal of HCN from 8, and the unusual sequence 5 → 12 in which the ring C enol ether of 5 is converted selectively into ring C diosphenol of 12. Key words: quassin, synthesis, selective base, diosphenols, acylation.

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