Diene Diels-Alder reactions

Khan F. A., Prabhudas B., Dash J. l,2,3,4-Tetrachloro-5,5-Dimethoxy-Cyclopenta-1,3-Diene Diels-Alder Reactions and Applications of the Products Formed J. Prakt. Chem. 2000 342 512-517... 

Chiral NHCs formed adducts with aldehydes that underwent enantioselective oxo-diene Diels-Alder reactions with enones.98 The NHC only needed to be added at 0.5 mol% to achieve yields >70% and ees in the high 90s. ... 

The usefulness of aminosiloxy diene Diels-Alder chemistry to the preparation of different substituted cyclohexenones is demonstrated in Table 11.3 The functionality at the 4 and 5-positions of the cyclohexenones can be easily controlled by the substitution pattern in the dienophile. The differing endo-exo selectivity found in the initial cycloadducts does not impact the usefulness of this route to cyclohexenones, since the amino group is eliminated in the last step. Chiral versions of aminosiloxy dienes provide the opportunity for asymmetric synthesis. Indeed, the diphenylpyrrolidine-substituted diene allows the synthesis of a variety of cyclohexenones, with good to excellent ee s 2b The usefulness of aminosiloxy diene Diels-Alder reactions to natural product synthesis is exemplified through the stereocontrolled synthesis of the pentacyclic indole alkaloid tabersonine 2c... 

Cycloaddition reactions involve the combination of two molecules to form a new ring. Concerted pericyclic cycloadditions involve reorganization of the Tr-electron systems of the reactants to form two new a bonds. Examples might include cyclodimerization of alkenes, cycloaddition of allyl cation to an alkene, and the addition reaction between alkenes and dienes (Diels-Alder reaction). 

Sol 2. (i) Butadiene sulfone or 3-sulfolene, a solid, is a convenient substitute for gaseous buta-1,3-diene. Diels—Alder reaction between buta-1,3-diene and dienophiles with low reactivity usually requires prolonged heating above 100 °C. This makes a procedure rather dangerous, if neat buta-1,3-diene is used, and requires special equipment for work under elevated pressure. Alternatively, buta-1,3-diene can be generated in situ by thermal sulfur dioxide extrusion from sulfolene, in which case no buildup of buta-1,3-diene pressure could be expected as the liberated diene is consumed in the cycloaddition, and, therefore, the equilibrium of the reversible extrusion reaction acts as an internal safety valve. ... 

Maleic anhydride grafting (cont.) poly(styrene-co-divinylbenzene), 694 poly(styrene-co-isobutylene), 675, 689 poly(styrene-co-nfialeic anhydride), 676, 679 poly(vinyl acetate), 676, 694 poly(vinyl acetate-co-vinyl fluoride), 678 poly(vinyl alkyl ethers), 675, 679, 692, 701 poly(vinyl chloride), 683, 692, 693, 695, 702 poly(vinylidene chloride), 691 poly(vinyl toluene-co-butadiene), 689 radical—initiated, 459-462, 464-466, 471, 475, 476 radiation—initiated, 459, 461, 466, 471, 474 redox-initiated, 476 rubber, 678, 686, 687, 691, 694 to saturated polymers, 459-466, 475, 476 solvents used 460-463, 465, 466, 469, 474-476 styrene block copolymers, 679 tall oil pitch, 678, 697 terpene polymers, 679, 700 thermally-initiated, 462, 464-467, 469, 476 to unsaturated polymers, 459, 466-474 vapor-phase techniques, 464, 474, 475 to wool fibers, 476 Maleic anhydride monomer acceptor for complex formation, 207-210 acetal copolymerization, 316 acetone CTC thermodynamic constants, 211 acetone photo-adduct pyrolysis, 195, 196 acetylacetone reaction, 235 acetylenic photochemical reactions, 193-196 acrylamide eutectic mixtures, 285 acylation of aromatic acids, 97 acylation of aromatics, 91, 92 acylation of fused aromatics, 92, 95, 97, 98 acylation of olefins, 99 acylation of phenols, 94-96 acylic diene Diels-Alder reactions, 104-111, 139 addition polymer condensations, 503-505 adduct with 2-cyclohexylimino-cyclopentanedi-thiocarboxylic acid, 51 adducts for epoxy resins curing, 507-510 adduct with 2-iminocyclopentanedithiocarboxylic acid, 51... 

Grignard reagent reactions, 233 halogen substitution, 60 handling-shipping-storage, 15 health considerations, 15 heat of polymerization, 244 heteroatom diene Diels-Alder reaction, 110, 111 heterocycles photochemical reactions, 182, 190 heterocycles radical reaction, 203, 204 heterocyclics-Diels-Alder reactions, 117, 127-131, 145... 

Scheme 14.21 Enantioselective, NHC-catalyzed oxo-diene Diels-Alder reactions.

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