scholarly journals Cycloadditionen, XX Thermisch induzierte intramolekulare Reaktionen bei 2-Methyl-2,3-butadienamiden / Cycloadditions, XX Thermally Induced Intramolecular Reactions of 2-Methyl-2,3-butadienamides

1992 ◽  
Vol 47 (12) ◽  
pp. 1785-1794 ◽  
Author(s):  
Gerhard Himbert ◽  
Hans-Jürgen Schlindwein
Keyword(s):  
Double Bond ◽  
Alder Reaction ◽  
Diels Alder ◽  
Secondary Amines ◽  
Thermally Induced ◽  
Methyl Group ◽  
Diels Alder Reaction ◽  
Intramolecular Reactions ◽  
Derivatives Of ◽  
Allenic Acid

The 2-methyl-2,3-butadienamides 4a—m are directly synthesized by the reaction of the corresponding allenic acid chloride 2 with the secondary amines 3. At heating, 4a—j undergo the intramolecular Diels-Alder reaction, by using their ω-standing double bond and the π-system of the directly bonded phenyl groups or of the “methylenic” bonded arenes or furans. Thereby the tricycles 6a—g (bearing five-membered lactam moreties) and/or the tricycles 7-9 (bearing six-membered lactam moreties) are formed. The influence of the geminai methyl group on the chemoselectivity and on the velocity of the IMDA reactions is investigated. The N-allyl derivatives of 4 (s. 41 and m) form the bicycles 10 by intramolecular [2+2]-Cycloaddition.

Cycloadditionen, XXII [1]. Synthese und thermische Reaktion von S-(Alkyl/Aryl)- 2.3-butadienthiosäure-estern / Cycloadditions, XXII [1]. Synthesis and Thermal Reaction of S-(Alkyl/Aryl)-2,3-butadienethioates

1994 ◽  
Vol 49 (4) ◽  
pp. 542-550 ◽  
Author(s):  
Gerhard Himbert ◽  
Dieter Fink
Keyword(s):  
Alder Reaction ◽  
Thermal Reaction ◽  
Diels Alder ◽  
Alkyl Aryl ◽  
Diels Alder Reaction ◽  
Ester Moiety ◽  
Derivatives Of

While the S-alkyl- or S-phenyl-2,3-butadienethioates 4 a-c are synthesized via the usual “Wittig ylide way”, the corresponding 2-methyl-2,3-butadienethioates 9 a-d and the 2-methyl-4.4-diphenyl-2,3-butadienethioates 9 e,f are obtained by condensation of the allenic acids 7 a,b with the thiols and thiophenols 8 in the presence of dicyclohexylcarbodiimide (DCC) and a catalytic am ount of 4-dimethylaminopyridine (DMAP). In contrast to N- or O-phenyl 2,3- butadienamides or -esters, resp., the phenyl derivatives of 4 and 9 do not undergo the intram olecular Diels-Alder reaction, but by heating, all representatives of 4 only decompose, while 9 a-d and 9 e,f rearrange to 3-alkyl(aryl)thio-2-cyclobuten-1-ones 12a-d and to 3-arylthio- 1-naphthols 14a, b, resp. Heating of the cyclobutenone 12d in the presence of N-methylaniline furnishes the 2-butenanilide 16. On reacting 1-phenylthio-1-propyne 17 with diphenylketene 18, the diphenylacetate 19 is isolated, where the naphthol derivative 14a represents the ester moiety.

Exploratory synthetic investigations related to 12a-deoxypillaromycinone

2002 ◽  
Vol 80 (6) ◽  
pp. 728-738 ◽  
Author(s):  
Lan Wang ◽  
Sanath K Meegalla ◽  
Cheng-Lin Fang ◽  
Nicholas Taylor ◽  
Russell Rodrigo
Keyword(s):  
Double Bond ◽  
Catalytic Hydrogenation ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
Step Procedure ◽  
Key Steps

Furfural is converted to suitably substituted AB synthon 21 for 12a-deoxypillaromycinone in 10 steps by a sequence involving the following key steps: intramolecular Diels-Alder reaction of a furan, 5-endo-trig cleavage of the oxabicyclo adducts 18, and catalytic hydrogenation of the double bond of a tetrasubstituted enone to produce 19. Enones 21a and 21b obtained by dehydrogenation of 19a and 19b, respectively, are then annulated with ethyl 2-methoxy-6-methylbenzoate in a four-step procedure to generate tetracyclic products 25 in 14 steps from furfural.

An examination of VANOL, VAPOL, and VAPOL derivatives as ligands for asymmetric catalytic Diels–Alder reactions

2006 ◽  
Vol 84 (10) ◽  
pp. 1487-1503 ◽  
Author(s):  
Douglas P Heller ◽  
Daniel R Goldberg ◽  
Hongqiao Wu ◽  
William D Wulff
Keyword(s):  
Asymmetric Catalysis ◽  
Methyl Acrylate ◽  
Lewis Acids ◽  
Alder Reaction ◽  
Diels Alder ◽  
Asymmetric Catalytic ◽  
Diels Alder Reaction ◽  
Positive Cooperativity ◽  
Derivatives Of ◽  
Methyl Phenyl

Several derivatives of the vaulted biaryl ligand VAPOL were prepared and evaluated as chiral ligands for aluminum Lewis acids in the catalytic asymmetric Diels–Alder reactions of methyl acrylate and methacrolein with cyclopentadiene. The substituents on VAPOL were introduced into the 6- and 6′-positions in an effort to further extend the chiral pocket of the major groove, which contains the phenol functions at the 4- and 4′-positions. The set of four new ligands that have been prepared have the following groups introduced into the 6- and 6′-positions of VAPOL: bromide, methyl, phenyl and 3,5-di-t-butylphenyl. All of these ligands give lower asymmetric inductions than the unsubstituted VAPOL for the Diels–Alder reactions of both methyl acrylate and methacrolein. The positive cooperativity of added carbonyl compounds on the autoinduction in the Diels–Alder reaction of methyl acrylate and cyclopentadiene were also investigated with the VANOL and VAPOL ligands as well as the 6,6′-dibromo and 6,6′-diphenyl derivatives of VAPOL. Only the reaction with VAPOL showed any significant positive cooperativity. The reaction with VANOL was sluggish at –78 °C, but at higher temperatures, the reaction did exhibit positive cooperativity that was similar to that of VAPOL. Finally, no positive cooperativity was observed with the VAPOL ligand for the reaction of methacrolein and cyclopentadiene.Key words: Diels–Alder, asymmetric catalysis, vaulted biaryl ligands, VANOL, VAPOL.

Diels-Alder Reaction Curing of Chlorobutyl Rubber by bis-Maleimides

1989 ◽  
Vol 62 (1) ◽  
pp. 42-54 ◽  
Author(s):  
K. Ho ◽  
R. Steevensz
Keyword(s):  
Zinc Oxide ◽  
Double Bond ◽  
Chain Length ◽  
Crosslinking Agent ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
Electronic Distribution ◽  
Curing Agents ◽  
Chlorobutyl Rubber

Abstract Different bis-maleimides are found to have different efficiencies and reactivities in the crosslinking of CIIR in the presence of zinc oxide. Although the degrees of crosslinking of CIIR by bis-maleimides cannot be defined absolutely, some trends concerning the efficiencies of the crosslinking are evident. In general, the aromatic bis-maleimides gave higher degrees of crosslinking than the aliphatic analogs. The reactivity and crosslinking efficiency of an individual bis-maleimide is very much affected by its end-to-end chain length and its electronic distribution, resulting from the interaction between the maleimide groups, and from the interaction between the maleimide groups and other functional groups present in the same molecule. The longer the bis-maleimide molecule and the more electron deficient the maleimido double bond, the greater its effectiveness as a crosslinking agent. Other curing mechanisms, possibly including polymerization of the maleimido groups, appear to be operative when using aromatic bis-maleimides as curing agents for CIIR.

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