Diels–Alder Reaction of Ethyl 3‐Benzamido‐2‐oxo‐6‐(trifluoromethyl)‐2H‐pyran‐5‐carboxylate with Alkoxyalkenes as an Effective Approach to Trifluoromethyl‐Containing 3‐Aminobenzoic Acid Derivatives

Abstract

Diels—Alder reaction of pyrone (I) with alkoxy alkenes at 120 °C provides the corresponding cycloadducts (III) and (IV).

Diels–Alder Reaction in the Synthesis of Fluorinated (Hetero)Aromatic Compounds

“…Introduction of electron withdrawing groups such as an ethoxycarbonyl function into the pyrone ring (compound 33 ) led to higher reactivity in Diels–Alder reaction and gave opportunity to investigate all intermediates of the process (Scheme ) …”

“…In contrast, both cis ‐ and trans ‐isomers of diene 35b are remarkably stable and could not be transformed to the corresponding aromatic product 36b by heating or microwave irradiation. However, elimination of ethanol occurred under reflux in the presence of TosOH …”

Supramolecular Diversity of Oxabicyclo[2.2.2]octenes Formed between Substituted 2H-Pyran-2-ones and Vinyl-Moiety-Containing Dienophiles

“…We have to stress that the crystal structures of the products 3 presented herein are the only 7oxabicyclo[2.2.2]octenes possessing a substituted amino group at one of the bridgehead atoms described so far, in addition to one publication (describing three structures) by Haufe et al, [22] and our own previous report [17]. It is interesting to note that in all cases where oxygen-based dienophiles 2 (i.e., 2a,b) were used, the only stereoisomer of the products 3 obtained was of the endo type; however, with the nitrogen-based dienophile (i.e., 6a) in one case (i.e., formation of 3f) only exo stereoisomer was obtained, whereas in the other case (i.e., formation of 3e) a mixture of both endo and exo stereoisomers was produced.…”

“…For example, in the case of cycloaddition between a substituted 3-acylamino-2H-pyran-2-one and ethyl vinyl ether [17] (or any other suitable alkene dienophile), in the first step a carbon-dioxide bridge system (i.e., 7-oxabicyclo[2.2.2]octene) is formed, such systems (including those formed via other reaction pathways) are known from the literature, but their solid-state structures were described just in a few cases, for some recent examples see ref. [18][19][20][21][22][23][24][25][26][27][28]. However, 7-oxabicyclo[2.2.2]octenes produced as described above can be formed as two possible regioisomers and each of these can exist as a mixture of two diastereoisomers (endo or exo), in turn each of the four distinctive possibilities is actually composed of a pair of enantiomers.…”

Inverse‐Electron‐Demand Diels–Alder Reactions of 2‐Pyrones: Bridged Lactones and Beyond

“…By adjusting the reaction conditions, bridged bicyclic adducts 51 , cyclohexadienes 52 and aromatic compounds 53 were achieved rapidly (Scheme 12 a). [15] Later, the authors expanded the substrate scope to cyclic vinyl ethers 30 . These cyclic vinyl ethers underwent IEDDA reactions with 45 a , providing an access to substituted dihydrobenzofurans 54 in good yields (Scheme 12 b).…”