Transannular Diels–Alder cyclization of a substituted 13-membered macrocyclic triene. An approach to the A.B.C.[6.6.5] rings of the Veratrum alkaloids

1992 ◽  
Vol 70 (9) ◽  
pp. 2335-2349 ◽  
Author(s):  
Miguel Quimpère ◽  
Luc Ruest ◽  
Pierre Deslongchamps
Keyword(s):  
Diels Alder ◽  
Oxygen Bridge ◽  
Veratrum Alkaloids ◽  
Tricyclic Compound

The synthesis and Diels–Alder cyclization of a substituted macrocyclic 13-membered triene 45 is described. Tricyclic compound A.B.C.[6.6.5] 46 having ring junctions of cis-anti-cis (CAC) stereochemistry was used to investigate the possibility of introducing a hemiketal oxygen bridge between positions 9 and 4 of the Veratrum alkaloid skeleton.

scholarly journals Stereocontrolled chiral synthesis of a trans-anti-trans tricycle by a transannular Diels–Alder reaction

1992 ◽  
Vol 70 (9) ◽  
pp. 2350-2364 ◽  
Author(s):  
Anne Marinier ◽  
Pierre Deslongchamps
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Chiral Synthesis ◽  
Diels Alder Reaction ◽  
Tricyclic Compound ◽  
Preliminary Study

The racemic and chiral synthesis of trans-cis-cis macrocyclic triene 5 is described. Heating this compound at 262 °C leads via a transannular Diels–Alder reaction to the tricyclic structure 6, which can be further transformed into tricyclic compound 7. This work constitutes a preliminary study for the synthesis of corticoids.

scholarly journals Diastereoselective intramolecular Diels–Alder reactions of the furan diene: the synthesis of (±)-1,4-epoxycadinane

1993 ◽  
Vol 71 (5) ◽  
pp. 611-622 ◽  
Author(s):  
Christine Rogers ◽  
Brian A. Keay
Keyword(s):  
Room Temperature ◽  
Furan Ring ◽  
Methylene Chloride ◽  
Membered Ring ◽  
Diels Alder ◽  
Methyl Group ◽  
Oxygen Bridge ◽  
Catalytic Quantity ◽  
The One

The diastereoselective intramolecular Diels–Alder reactions of the furan diene (IMDAF), in which the side arm comprises four carbon atoms and is substituted by a methyl group adjacent to, or one carbon removed from, the furan ring, are described. Adducts are formed in moderate to excellent yields when treated with either Florisil in methylene chloride at room temperature or methylaluminum dichloride in methylene chloride at −78 °C. Florisil is most effective for substrates containing unsubstituted dienophiles. An equimolar quantity (1.1 equivalents) of methylaluminum dichloride is most effective for precursors having methacrolein-type dienophiles, while a catalytic quantity (0.1 equivalent) is effective for crotonaldehyde-type dienophiles. Only the adducts with the side arm orientated syn with respect to the oxygen bridge are detected and isolated. The major diastereomer is the one in which the methyl group (initially on the side arm) is situated equatorially on the newly formed six-membered ring. An application of the diastereoselective IMDAF reaction to the synthesis of (±)-1,4-epoxycadinane is described, beginning with 2-methylfuran.

A,B-Diheteropentalenes by a Tandem Intramolecular Diels-Alder/Reverse Diels-Alder Reaction Sequence. Application to the Synthesis of Thieno[3,4-b]furan

1995 ◽  
Vol 48 (3) ◽  
pp. 593 ◽  
Author(s):  
JH Buttery ◽  
J Moursounidis ◽  
D Wege
Keyword(s):  
Furan Ring ◽  
Alder Reaction ◽  
Ring System ◽  
Diels Alder ◽  
Coupling Constants ◽  
Reaction Sequence ◽  
Acetylenic Ester ◽  
Diels Alder Reaction ◽  
Tricyclic Compound ◽  
Hydrolysis Of

Alkylation of 2-furylmethanethiol (28) with propargyl chloride gave the thioether (22) which on methoxycarbonylation afforded the acetylenic ester (30). On heating, this material underwent an intramolecular Diels -Alder reaction to give the tricyclic compound (32). In the presence of 3,6- di (pyridin-2′-yl)-s- tetrazine , (32) afforded methyl 4,6-dihydrothieno[3,4-b]furan-3-carboxylate (38) by a sequence involving a further Diels -Alder reaction followed by two reverse Diels-Alder reactions. The ester (38) could be dehydrogenated to give methyl thieno [3,4-b]furan-3-carboxylate (40) while hydrolysis of (38), followed by decarboxylation and dehydrogenation delivered the parent thieno [3,4-b]furan (5). 3-Methyl-4,6-dihydrothieno[3,4-b]furan (46) and 3-methylthieno[3,4-b]furan (47) were prepared; a comparison of the 4JMe-C=C-H coupling constants in the 1H n.m.r . spectra of (46) and (47) suggests that an increase in the C2-C3 furyl bond order accompanies the (46) → (47) conversion. Methyl 4,6-dihydrofuro[3,4-b]furan-3-carboxylate (39), 4,6-dihydrofuro[3,4-b]furan (27) and methyl 4,6-dihydro-6-phenylfuro[3,4-b]furan-3-carboxylate (53) were prepared by an analogous tandem reaction sequence. These compounds could not be dehydrogenated to the fully conjugated furo [3,4-b]furan ring system.

scholarly journals The effect of Lewis acids on the intramolecular Diels–Alder reaction of the furan diene

1992 ◽  
Vol 70 (12) ◽  
pp. 2929-2947 ◽  
Author(s):  
Christine Rogers ◽  
Brian A. Keay
Keyword(s):  
Carbon Atom ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Alder Reaction ◽  
Diels Alder ◽  
Oxygen Bridge ◽  
Excellent Yield ◽  
Diels Alder Reaction ◽  
Alkyl Groups ◽  
General Method

A general method is described for effecting the intramolecular Diels–Alder reaction of the furan diene in which the side arm connecting the diene to the dienophile contains four carbon atoms. The use of 1.1 equivalents of methylaluminum dichloride at −78 °C for 2–8 h shifts the Diels–Alder equilibrium towards the products and provides the oxatricyclo adducts in good to excellent yield. Catalytic quantities of methylaluminum dichloride (10 mol%) provided a higher quantity of adduct than excess Lewis acid when the enone was substituted with alkyl groups. The scope was extended to include a precursor containing a five carbon atom side arm, and two examples containing acetylenic dienophiles that were activated by a carbonyl moiety on the side arm. Precursors having a four carbon atom side arm provided only oxatricyclo adducts having the side arm syn to the oxygen bridge. The assignment of the stereochemistry of the oxatricyclo adducts is discussed in detail.

Stereocontrolled construction of A.B.C.[6.6.6] tricycle via transannular Diels–Alder reaction of 14-membered macrocycle with acetylene as dienophile

1990 ◽  
Vol 68 (12) ◽  
pp. 2137-2143 ◽  
Author(s):  
Yao-Chang Xu ◽  
Michel Cantin ◽  
Pierre Deslongchamps
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
The Other ◽  
One Pot ◽  
Diels Alder Reaction ◽  
Other Hand ◽  
Tricyclic Compound ◽  
Stereocontrolled Synthesis ◽  
Allylic Chloride

The syntheses of the acyclic dienynes 14a (cis-trans-acetylene) and 14b (trans-trans-acetylene) are described. The tandem macrocyclization and transannular Diels–Alder reaction of the allylic chloride 14b was conducted in the presence of Cs2CO3 at 85 °C in one-pot to provide tricyclic product 16, with the two hydrogens in ring B being cis. On the other hand, treatment of the allylic chloride 14a under the same conditions afforded 14-membered macrocycle 17, which could be transformed at 250 °C into a similar tricyclic product 18 with the two hydrogens in ring B being trans, along with an interesting by-product 19. The mechanism for the formation of 19 is also discussed. Keywords: stereocontrolled synthesis, macrocycle, tricyclic compound, transannular Diels–Alder reaction.

Stereocontrolled construction of A.B.C.[6.6.6] tricycle via transannular Diels–Alder reaction of 14-membered triene macrocycle

1990 ◽  
Vol 68 (12) ◽  
pp. 2144-2152 ◽  
Author(s):  
Michel Cantin ◽  
Yao-Chang Xu ◽  
Pierre Deslongchamps
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Excellent Yield ◽  
Diels Alder Reaction ◽  
Tricyclic Compound ◽  
Stereocontrolled Synthesis

The synthesis of the four acyclic trienes 11a, b and 20a, b is reported. The tandem macrocyclization and stereoselective transannular Diels–Alder reaction of acyclic trienes 11b (trans-trans-cis) and 20b (trans-trans-trans) were observed in the presence of Cs2CO3 at 85 °C to give tricycles 30 (TST) and 32 (CAT) respectively. However, treatment of acyclic trienes 11a (cis-trans-cis) and 20a (cis-trans-trans) under the same conditions yielded the 14-membered macrocycles 21 and 23, which were stereoselectively transformed at 250 °C into tricycles 22 (CST) and 24 (CAT) respectively in excellent yield. Keywords: stereocontrolled synthesis, macrocycle, tricyclic compound, transannular Diels–Alder reaction.

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