The Retro–Diels–Alder Reaction PartII. Dienophiles with One or More Heteroatom

Abstract

This review (Part II) is topically organized around the dienophile that is generated in a retro [4 + 2] reaction, and to the extent possible follows the principles adopted for Part I, which covers reactions in which both dienophile bonding centers are carbon atoms. The present chapter encompasses retro–Diels–Alder (rDA) reactions in which one or both of the dienophile reaction centers are heteroatoms. Any of the other atoms in the starting material (cycloadduct) may be carbon or heteroatom. Substituents on all positions are encompassed, and any bond order available to any oxidation state of an element is included, as is bonding to non‐nearest neighbor atoms (e.g., bicyclics). The reader is directed to Part I (Vol. 52) for general discussion of the rDA reaction, the features that affect rates and outcome, and the use of acids, bases, other catalysts, and scavengers. Certain subclassifications (e.g., processes proposed under MS conditions, polymer applications) of rDA reactions have been omitted from both sections; these topics are listed in the Introduction to Part I. Citations to over 100 reviews on various aspects of the rDA reaction are collected at the beginning of the References to Part I. Those that are especially pertinent to Part II will be repeated here, in the context of the particular dienophile under discussion. The decision to split the review of the rDA reaction into two parts was based on the volume of literature encountered, as outlined in the Introduction to Part I. Active literature searching was concluded for both Parts in April 1995, although occasional more recent references have been included.

Rhodium-Catalyzed Decarboxylative and Dehydrogenative Coupling of Maleic Acids with Alkynes and Alkenes

“…15 Oil , 7, 22.2, 29.1, 32.2, 114.7, 116.2, 128.4, 128.7, 129.8, 132.5, 147.0, 158.0, 162.2 13.6, 22.3, 29.7, 31.2, 113.0, 117.9, 127.9, 128.8, 128.9, 136.0, 146.9, 162.5, 163.2 Ethyl 2-Oxo-6-phenyl-2H-pyran-5-calboxylate (3j). Oil, 49 mg (40%); hexane−ethyl acetate 90:10 (v/v, eluent); 1 H NMR (400 MHz, CDCl 3 ) δ 1.09 (t, J = 7.…”

“…15 Mp 66−67°C (yellow solid), 27 mg (80%); hexane−ethyl acetate 75:25 (v/v, eluent); 1 H NMR (400 MHz, CDCl 3 ) δ 6.29 (dd, J = 0.9, 9.2 Hz, 1H), 6.67 (dd, J = 0.9, 6.9 Hz, 1H), 7.41−7.47 (m, 4H), 7.80−7.85 (m, 2H); 13 C NMR (100 MHz, CDCl 3 ) δ 101. 0, 114.0, 125.6, 128.9, 130.9, 131.3, 143.7, 161.1, 162.0; HRMS m/z Calcd for C 11 H 8 O 2 (M + ) 172.0524, found 172.0523.…”

“…; HRMS m/z Calcd for C15 H 16 O 2 (M + ) 228.1150, found 228.1153. 6-(n-Butyl)-5-phenyl-2(2H)-pyran-2-one (3i′).…”

Dearomative dihydroxylation with arenophiles

“…Although similar unsaturated bicyclic urazoles are known to undergo thermal cycloreversion 31 , no reaction was observed on heating cycloadducts 3 or 4 to temperatures up to 250 °C. Therefore, we decided to examine a one-pot urazole hydrolysis/bicyclic hydrazine oxidation sequence that would generate dihydrodiols via the extrusion of molecular dinitrogen.…”

Diels-Alder Chemistry to Develop Self-Healing Epoxy Resins and Composites Thereof

“…Several reversible bonds have been used to achieve self-mending functionality. Hydrogen bonds, Van der Waals forces, and electrostatic interactions in polymeric ionomers [11] are claimed to explain self-repair features in supramolecular structures, while covalent disulfide bridges [12], ester linkages [13], alkoxyamine moieties [14], and Diels-Alder bonds [15,16] account for damage recovery in cross-linked structures. Among them, Diels-Alder chemistry has been widely adopted because of its simplicity, high efficiency, and repeatability through only the application of heat.…”