Site-Selective Diels−Alder Reactions of 7-(Methoxyimino)-4-methylchromene-2,8-dione with Alkenes (original) (raw)
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2002
Chapter 1 overviews the general concepts of the Diels-Alder reaction, and particular attention is given to the inverse-electron-demand Diels-Alder reaction (IEDDA). Examples of all-carbon diene systems that contain electron-withdrawing groups at their 1- and 3-positions and their IEDDA reactivity are described. -- Chapter 2 presents the synthesis of a coumarin-fused diene that was produced in a single step. An oxidative cleavage of this diene produces 3-formylcoumarin, which can be used in the Homer-Wadsworth-Emmons reaction or the Knoevenagel condensation to afford other coumarin-fused dienes. -- Chapter 3 presents the IEDDA reactivity of methyl (E)-3-(2-oxo-2H-chromen-3-yl)acrylate with electron-rich dienophiles. Enamines undergo an IEDDA-driven domino reaction to produce benzocoumarins. The reaction procedure can be simplified by generating the dienophile in situ. -- Chapter 4 details the methodology development of the IEDDA-driven domino reactions. The methodology was used to sy...
4-Styrylcoumarins and 2,3-Dimethylquinoxaline in Diene Syntheses
Journal of the American Chemical Society, 1955
Acetylation of 88 mg. of the diol with acetic anhydridetemperature furnished 79 mg. of the corre-Acetylation (room temperature) of 70 mg. of this material led, after one recrystallization from ether, to 66 mg. of methyl diacetylmachaerinate (VIc), m.p. 278-280'; identity was established in the usual manner by mixture melting point and infrared comparison. Attempts to establish a difference in the reactivity of the C, 76.21; H , 10.10. pyridine at sponding diacetate, m.p. 252-259", [ c Y ]~~D f31".
Tetrahedron, 2003
Benzyl-3-(bromomethyl)-2(1H)-pyrazinone was converted to [3,4-c] sulfolene pyridinone 8a and further (1-or 3-) substituted derivatives having a dienophilic side chain on the sulfolene ring. Thermolytic extrusion of sulfur dioxide from o-QDM precursor 8 led to generation of 3,4-dimethylene-2(1H)-pyrazinone 9, which was reacted in situ with various dienophiles. Thermolysis of the substituted precursors resulted in intramolecular cycloaddition of the corresponding o-QDM intermediates q 2003 Elsevier Science Ltd. All rights reserved.
Reactions of 3-carbomethoxy-2-aza-1, 3-butadiene derivatives with dienophiles
The reactions of l,l-diphenyl-3-carbomethoxy-2-aza-1,3-butadiene derivatives la-e (on C4 : H,H or H&H3 or H,CgHS, both E and Z isomers), and of the C4 unsubstituted 1 -phenyl-1 -ethoxy analogue 2, were studied with a number of electron-rich and electron-poor dienophiles, with results showing that la-e give heterocycloadducts in Diels-Alder reactions with electron-poor dienophiles. Michael adducts were obtained from the EtAlC12 catalyzed reactions of these compounds with dimethyl acetylendicarboxylate. Compound 2 gave heterocyclic adducts as well but behaved like a nucleophile. at least in the case of the reactions with dimethyl acetylendicarboxylate and ethyl propynoate: these reactions afforded 2-axatrienes as Michael adducts that gave pyridine derivatives upon heating. The synthesis of the new l-ethoxy-2-axa-1,3-butadiene 2 is also reported.
Helvetica Chimica Acta, 1981
The preparations of 1-acetylvinyl arenecarboxylates H2C=C (COCH,)OCOR with R = phenyl, p-nitrophenyl, 2,4-dinitrophenyl, u-and P-naphthyl are described (3). The Diels-A Ider reactivity of these dienophiles toward cyclopentadiene is evaluated and compared with that of methyl vinylketone, 3-trimethylsilyloxy-, 3-ethoxy-and 3-acetoxy-3-buten-2-ones. The stereoselectivity of the cycloadditions of these dienophiles with 2,3,5,6-tetramethylidene-7-oxanorbornane (1) and 5,sdimethoxy-l,4-epoxy-2,3-dimethylidene-I, 2,3,4-tetrahydroanthracene (2) is studied. In principle, the dienophiles 3 allow direct functionalization of the position C(9) of the A-ring of daunomycinone analogs by Diels-Alder additions to exocyclic dienes such as 1 and 2. Introduction.-Anthracyclinones are aglycones of very important antibiotics and anti-tumor drugs [l]. They can be prepared readily [2] [3] by two successive 3a-i R' 1 2a R1=R2=OCH3 R = a Me3Si f 2,4-(NO2)2-C6H3CO h RI=R2=H b Et g a-naphthyl-CO c R1=OCH3, R2=H c CH3CO h 8-naphthyl-CO d C~H S C O i CH3 e 4-(N02)-C6HdCO j H Diels-Alder additions [4] to 2,3,5,6-tetramethylidene-7-oxanorbornane (1) [5]. The A-ring of daunomycinone (4) [6] bears a hydroxy group at C(9), adjacent to the carbonyl function of the side-chain. This OH group can be introduced, in principle I)
Catalytic Enantioselective Diels−Alder Reactions of 1,4-Quinone Monoketals
Organic Letters, 2001
Trimethyl-1,5-dioxa-spiro[5.5]undeca-7,10-dien-9-one (2a): To a solution of 2,2-dimethyl-1,3-propanediol (1.04 g, 10.0 mmol) in CH 2 Cl 2 (9 mL) were added o-cresol (104 µL, 108 mg, 1.00 mmol) and [bis(trifluoroacetoxy)iodo]benzene (946 mg, 2.20 mmol) at room temperature. The reaction mixture immediately turned black and then orange over a period of 30 min. Et 2 O (50 mL) was added and the reaction mixture was extracted with a sat. NaHCO 3 solution (50 mL) and brine (50 mL). After drying over Na 2 SO 4 , the 1,4-quinone monoketal 2a (125 mg, 648 µmol, 65%) was obtained by column chromatography [deactivated silica gel (5% NEt 3), hexane:Et 2 O 100:0→5:1] as a colorless solid, mp
Tetrahedron Letters, 2009
O-Methyl-4-coumarincarbaldehyde oxime reacted as an azadiene with electron-deficient and electronrich dienophiles to give, via one-step hetero-Diels-Alder cycloaddition reactions, the corresponding 5H-coumarin[4,3-c]pyridin-5-ones. When excess of the dienophile was used, fused azatetracyclo derivatives were also formed via a tandem Diels-Alder and 1,3-dipolar cycloaddition reaction of the dienophile to an azomethine ylide formed by the intermediate 2,3-dihydro-5H-coumarin[4,3-c]pyridine-5-one. The regio-and stereoselectivities of the new compounds correspond well with spectroscopic (2D NMR) and theoretical data. A possible mechanistic scheme is provided.
Studies into the generation and Diels–Alder reactions of 7,8-quinolyne with furan dienes
Tetrahedron Letters, 2005
Reaction of an appropriate ortho-halo tosylate precursor with organolithium reagents provides the first conclusive route to the intermediate, 7,8-quinolyne. The transient existence of this hetaryne was confirmed by Diels-Alder reactions with furan derivatives that provide endoxide adducts. Chemical induced rearrangement of these adducts allows entry to key compounds of 10-hydroxy[h]benzoquinoline and its 7-substituted derivatives in modest yields. Published by Elsevier Ltd.