Influence of Lewis Acids on the Diels–Alder Reaction. V. The Reaction of Furan with Dimethyl Acetylenedicarboxylate

Abstract

The Diels-Alder addition of furan to dimethyl acetylenedicarboxylate (DMAD) affords a monoadduct 1. The position and steric course of further addition of furan to the latter are temperature dependent. At temperatures of 50" or below addition occurs mainly at the activated double bond to give et~do-endo 4 and endo-exo 5 diadducts. At 100" addition occurs at the less substituted double bond of the monoadduct to give analogous etrdo-endo 7 and endo-exo 9 diadducts; further addition of furan to the latter at 100' affords four triadducts 12-15. The configurations of all these products were determined by p.m.r. and assignments confirmed by simulation of the spectra.AICI, causes enormous rate enhancement of the Diels-Alder additions of furan to DMAD and to the activated double bond of the monoadduct. In the presence of the Lewis acid the predominant diadduct formed is the endo-exo isomer 5.L'addition du type Diels-Alder du furanne sur I'acCtylenedicarboxylate de dimithyle (DMAD) conduit au produit de monoaddition 1. La positio~l et le mecanisme sterique d'additions supplCmentaires du furanne sur le produit 1 dependent de la temperature. A 50 "C ou en-dessous I'addition se produit principalement sur la double liaison activee pour donner des produits de double addition endo-endo 4 et endo-exo 5. A 100 "C, I'addition se produit sur la double liaison la moins substituie du produit de monoaddition pour donner les produits de double addition analogues et~do-endo 7 et endo-exo 9; des additions supplCmentaires du furanne sur ces derniers produits a 100 "C conduisent a quatre produits de triple addition 12-15. Les configurations de tous ces produits ont CtC dCterminCes par r.m.n. e t les attributions ont CtC confirmkes par simulation des spectres.Le AICI, entraine une augmentation enorme de la vitesse d'addition du type Diels-Alder du furanne sur le DMAD et sur la double liaison activke du oroduit de monoaddition. En oresence de I'acide deLewis. Ie produit majeur de double addition form6 est l'isomkre etldo-e.ro 5.

Ring-Chain Equilibrium between an [18]Cyclacene Derivative and a Ladder Oligomer

“…With these structures at hand the NMR spectra of 16 could be assigned and this assignment was then used in turn to establish the structures of exo-7 and endo-7. This assignment is consistent with the fact that oxanorbornenes (like 6) tend to add dienes from the oxygen side [8] and dienes of type 4 prefer to add dienophiles from the less crowded side with respect to the hexamethylene loop. [9] A further question of interest was the spatial shape of exo-16 in solution.…”

“…[2e] using an [8]cy-BuLi in the presence of furan gave 8 as a mixture of two clacene derivative. We here report on the synthesis of the isomers (by NMR spectroscopy, cis and trans with respect multicyclic compound 11 whose thermal treatment liberates to the oxygen bridges) in 65% yield.…”

A density functional theory study of the reactions of furans with substituted alkynes to form oxanorbornadienes and subsequent [4 + 2] and [2 + 2 + 2] addition reactions

“…[ 20 ] McCulloch et al rationalized Kallos and Deslongchamps's observation and confirmed the reversible nature of the Diels–Alder cycloaddition. [ 21 ] It is reported [ 22 ] that due to the aromacity of the furan ring, the Diels–Alder reactions of furans and acetylenes are rather sensitive thermally and revert to the starting materials. Also, it was suggested that only with the use of very reactive dienophiles such as maleic anhydride or dimethyl acetylenecarboxylate can respectable yields of cycloadduct be attained (Scheme 3).…”

Container Systems II: An Experimental Study of the High‐Pressure Intramolecular Cycloaddition of Tethered Furans and Anthracenes onto Norbornane Cyclobutene‐1,2‐diesters

“…The rationale for this approach is based on the known reaction of furan with DMAD to form sesquinorbornadienes (Table ). This reaction has several features that are potentially useful for this application: (i) the reaction can be conducted under thermal, Lewis‐acid catalysis, or high‐pressure; (ii) different products or ratios of products are formed under the different conditions (Table ); and (iii) the reaction is reversible. In particular, specific stereostructures may be better suited for cyclization and the reversibility of the reaction can be used to recycle the non‐cyclic products.…”