Photochemisches Verhalten von 1- und 2-alkylierten 1, 2-Dihydronaphthalinen bei tiefen Temperaturen

The irradiations of 1, 1-dimethyl- (8), 1, 1-di-(tri-deuteriomethyl)- (d₆– 8 ), 1, 1, 2, 2-tetramethyl- ( 9 ) and cis- and trans-1, 2-dimethyl-1, 2-dihydronaphthalenes (cis- and trans- 10 ) were investigated in 2, 2-dimethylbutane/pentane at ?100° using a mercury high-pressure lamp, and with mercury high- and low-pressure lamps at room temperature. The results were compared with one another, and those of the individual compounds are collected in schemes 2 and 4–7. The most important results are the following: 1. The 1, 2-dihydronaphthalenes undergo a conrotatory ring opening to the o-quinodimethanes on irradiation with high- or low-pressure lamps at room temperature or at ?100°. Thermal reactions ([1, 7a]H-shifts, electrocyclisations) are suppressed at ?100°. The o-quinodimethanes formed from 8 (scheme 2), 9 (scheme 5) or cis- 10 (scheme 6) undergo on irradiation with the high-pressure lamp, [1, 5]H-shifts or photochemical Diels-Alder reactions after renewed photochemical excitation, to yield the benzobicyclo[3.1.0]hex-2-ene derivatives. These Diels-Alder reactions do not proceed stereospecifically, and therefore are not orbital symmetry controlled reactions. 2. If the 1, 2-dihydronaphthalenes are irradiated at room temperature with either a high- or a low-pressure lamp, then the initially formed o-quinodimethanes undergo thermal [1, 7a]H-shifts, in preference to all other reactions, as long as this is sterically possible; the resulting products can undergo secondary photochemical transformations. Such o-quinodimethanes are formed on irradiation of 8, 9 and cis- 10 . From trans- 10 , an o-quinodimethane mixture is formed, of which one component (cis, cis- 22 ) undergoes thermal [1, 7a] H-shifts, while the other (trans, trans- 22 ) suffers a thermal disrotatory electrocyclisation to give cis- 10 . If a high-pressure lamp is used in the last experiment, then the competing photochemical Diels-Alder cyclisation to bicyclic compounds of the type 23 (scheme 7) can result in the trans, trans- 22 . As was shown by Salisbury [3], and confirmed by ourselves in other cases [2], photochemical Diels-Alder reactions or [1, 5]H-shifts in the o-quinodimethanes require light of wavelength ? 400 nm (high-pressure lamp). The present photochemical investigations amplify and confirm our earlier conclusions concerning the photochemistry of the 1, 2-dihydronaphthalenes [2].     

Diels-Alder-Reaktionen von 2,4-Bis{[(tert-butyl)dimethylsilyl]oxy}-3-aza-1,3-pentadien mit Heterodienophilen

Diels-Alder Reactions of 2,4-Bis{[(tert-Butyl)dimethylsilyl]oxy}-3-aza--1,3-pentadien with Heterodienophiles The 2,4-bis{[(tert-butyl)dimethylsilyl]oxy}-3-aza-1,3-pentadien( 2 ) reacts via the Diels-Alder adducts 3 , 6a-c , and 8a , b , which cannot be isolated, giving the triazines 4 , 7a-c , and the oxadiazines 9a , b . The hydrolysis of 4 in MeOH affords the N-acetyl-acetamid derivative 5 . The formula of 9a is proven by an X-ray-structure analysis.     

Total Synthesis of (±)-2-Pupukeanone

(±)-2-Pupukenone ( 4 ) has been synthesized, the key step being the intramolcular Diels-Alder reaction of the intermediate 13 to 14 (42%) and 15 (14%). The bromodiene 12 has been obtained from the reaction of α-isopropylidene-γ-lactone (Scheme 2) 12 with sodium phenylselenide and subsequent esterification to 9 , oxidation and thermal elimination of which furnished 10 . Reduction of 10 with diisobutylaluminimum hydride and treatment of the resulting alcohol 11 with PBr₃ led to the required bromodiene 12 . Finally, hydrogenation of the 14 on Pt(C) in CH₃OH gave a 4:1 mixture of 2-pupukeanone ( 4 ) and epi-2-pupukeanone 16 .     

Face selectivity of the Diels-Alder additions and cheletropic additions of sulfur dioxide to 2- vinyl-7-oxabicyclo[2.2.1]hept-2-ene derivatives

Racemic 6-ethenyl-7-oxabicyclo[2.2.1]hept-5-en-2-one ( 23 ), 5-ethenyl-7-oxabicyclo[2.2.1]hept-5-en-2-one ( 25 ) and their ethylene acetals 24 and 26 , respectively, were derived from the Diels-Alder adduct of furan to 1-cyanovinyl acetate ( 27 ). The Diels-Alder additions of 26 to dimethyl acetylenedicarboxylate, to methyl propynoate, to N-phenylmaleimide, and to methyl acrylate were highly exo-face selective, as were the cycloadditions of methyl propynoate to dienones 23 and 25 and of dimethyl acetylenedicarboxylate to ethylenedioxy-diene 24 . The cheletropic additions of SO₂ to 23 – 26 gave exclusively the corresponding sulfolenes 57 – 60 resulting from the exo-face attack of the semicyclic dienes under conditions of kinetic and thermodynamic control.     

Diastereoselective Diels-Alder Reaction of 2-Thienyl and 2-Furyl Substituted 3-Propenethioamides with Electron Deficient Dienophiles

Summary. The hetero-Diels-Alder reaction of N-aryl-3-(2-thienyl)-2-propenethioamides with N-phenylmaleimide and maleimide yielded a mixture of endo- and exo-2-arylimino-4-(2-thienyl)tetrahydrothiopyran[2,3-c]pyrroles. Cycloaddition to diethyl fumarate required acylation and furnished a mixture of diastereoisomeric 5-(N-acetylphenylamino)-2,3-bis-(ethoxycarbonyl)-4-(2-thienyl)-3,4-dihydro-2H-thiopyrans. Reactions of 3-(2-furyl)-2-propenethioamides with N-arylmaleimides furnished the correspondent 2-arylimino-4-(2-furyl)tetrahydrothiopyran[2,3-c]pyrroles. In the cycloadditions of the heterodienes with N-arylmaleimides the endo-cycloadducts were formed as the major products.     

Synthesis of functionalized 3,4-dihydro-2H-pyrans by hetero —Diels-Alder reaction of an enaminoketone with enol ethers

Summary The hetero —Diels-Alder reaction of 3-(N-acetylbenzylamino)-2-cyano-1-phenyl-2-propen-1-one (3) with enol ethers (4) leads to diastereoisomeric cycloadducts5 and6 in good yields. The structure of the products is discussed in terms of configuration and preferred conformation. Reaction of5 with sulfuric acid yields 3-benzoyl-1,2-dihydropyridin-2-one (7).

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Synthese funktionalisierter 3,4-Dihydro-2H-pyrane durch Hetero —Diels-Alder — Reaktion eines Enaminoketons mit Enolethern

Zusammenfassung Die Hetero —Diels-Alder — Reaktion von 3-(N-Acetylbenzylamino)-2-cyano-1-phenyl-2-propen-1-on (3) mit Enolethern (4) führt in guten Ausbeuten zu den diastereomeren Cycloaddukten5 und6. Die Strukturen der Produkte werden im Zusammenhang mit ihrer Konfiguration und Vorzugskonformation diskutiert. Die Reaktion von5 mit Schwefelsäure liefert 3-Benzoyl-1,2-dihydropyridin-2-on (7).

     

Hetero-Diels-Alder reaction of propenenitriles with enol ethers: a convenient approach to functionalized 3,4-dihydro-2H-pyrans

The hetero-Diels-Alder reaction of 3-(N-acetyl-N-benzylamino)-2-formylprop-2-enenitrile with enol ethers yielded cis/trans diastereoisomers of 2-alkoxy-4-amino-3,4-dihydro-2H-pyran-5-carbonitriles in moderate yields. Acidic hydrolysis of cis-diastereoisomer in concentrated sulfuric acid gave 2-oxo-1,2-dihydropyrydine-3-carbaldehyde. The reaction of 2-benzoyl-3-heteroaromaticprop-2-enenitriles with enol ethers afforded diastereoisomeric cis/trans cycloadducts in good yields. The structure of the products is discussed in terms of configuration and preferred conformation.     

Azasteroids. Synthesis by Diels-Alder Reaction between Maleimides, Citraconimide, and Triazolindiones and 1-(1-Trialkylsiloxyvinyl)-3,4-dihydronaphthalene Derivatives

Summary. 18-Nor-16-azaestrane derivatives with 8β, 13β, and 14β orientation were isolated from Diels-Alder reactions between maleimides or citraconimide and 1-(1-siloxyvinyl)naphthalene derivatives. (8RS)-13,14,16-Triazaestrane derivatives were synthesized from 1,2,4-triazolin-3,5-diones. The parent 11-oxo derivatives were obtained by desilylation, and they were transformed into 11-hydroxyimino derivatives. 3-Hydroxy derivatives, finally were synthesized by cleavage of the 3-methoxy group with BBr₃. During these transformations the stereochemistry of the steroidal skeleton was not changed. The stereochemistry of these “unnatural” steroids was elucidated by spectroscopic methods, and compared with results from calculations, and with the configuration of natural estrane derivatives. Finally, an improved method for the synthesis of the starting material, 6-methoxy-1-[(1-trialkylsiloxy)-vinyl]-3,4-dihydronaphthalene was developed.     

New Dienophiles: 1-Acetylvinyl Arenecarboxylates. Reactivity toward cyclopentadiene and exocyclic dienes

The preparations of 1-acetylvinyl arenecarboxylates H₂C=C(COCH₃)OCOR with R = phenyl, p-nitrophenyl, 2,4-dinitrophenyl, α- and β-naphthyl are described (3) . The Diels-Alder 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 5,8-dimethoxy-1,4-epoxy-2,3-dimethylidene-1,2,3,4-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 .     

Zur Synthese von 1-(3,3-Dimethyl-2-norbornyl)-äthanon

An improved synthesis of the title compound (1) is described. The catalytical action of variousLewis acids on the sterically hinderedDiels-Alder reaction of mesityl oxide with cyclopentadiene has been investigated. The mixture ofendo- andexo-isomers of the unsaturated intermediate2 yielded pure1 on hydrogenation and isomerization by sodium methoxide. The proof of theexo-configuration of the acetyl group has been achieved by mass spectra and 100 MHz¹H-NMR spectra.

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Herrn Prof. Dr.M. Pailer mit den besten Wünschen zum 65. Geburtstag gewidmet.     

Synthesis of (±)-4-Demethoxydaunomycinone by Double Diels-Alder Additions to 2, 3, 5, 6-Tetramethylidene-7-oxanorbornane

Sequential Diels-Alder additions of methylvinyl ketone and dehydrobenzene to 2, 3, 5, 6-tetramethylidene-7-oxanorbornane (4) yielded the (5, 12-epoxy-1, 2, 3, 4, 5, 6, 11, 12-octahydro-2-naphtacenyl) methyl ketone (10) which, in few steps was oxidized to a precursos of (±)-4-demethoxydaunomycinone. The preparations of two precursors of anthracyclinones, the (5-acetoxy-) and (12-acetoxy-1, 2, 3, 4-tetrahydro-2-naphtacenyl) methyl ketones (14, 15) are presented. The synthesis of 6, 13-epoxy-6, 13-dihydropentacene (8) is also reported.     

4- und 5-Nitro-benzo[c]thiophen: Reaktionen mit CC-Dienophilen. Synthese von funktionalisierten und anellierten 7-Thia-bicyclo[2.2.1]heptenen — Struktur und Reaktivität voniso-anellierten Systemen mit 4nπ- und (4n+2)π-Elektronen, 19. Mitt.

Summary 4- and 5-nitro-benzo[c]thiophenes react as heterocyclic dienes with N-substituted maleic imides. [4+2] cycloaddition gives rise to the formation ofendo, exo configuratedDiels-Alder adducts. This efficient transformation can be utilized for the synthesis of benzo-annelated 7-thiabicyclo[2.2.1]heptenes. Their spectroscopic data are reported and compared with those of the [4 + 2] adducts of isoelectronic 4-(5)-nitro-2-tert-butyl-2H-isoindoles.

     

Formal Total Synthesis of (+)-Dihydromevinolin via a Chelate-Controlled Intramolecular Diels-Alder Reaction as the Key Step

Compound 3 was synthesized efficiently from enone 4 via (silyloxy)cyclopropanecarboxylate intermediates 6 and 7 . A chelate-controlled intramolecular Diels-Alder reaction of 3 afforded the octahydronaphthalene-2-carboxylate isomer trans- 2b as the main product. This compound was stereoselectively converted into the known dihydromevinolin precursor 1 , thus providing a formal total synthesis of this natural product.     

3-(Prop-2-enylidene)azetidin-2-one Derivatives: Synthesis,structure, and formation of 3-spiro-β-lactams via Diels–Alder reactions

Reactions of 3-silylated β-lactams ( 1 ) with α,β-unsaturated ketones give the propylidene-β-lactams 3 and the cycloalkenylidene derivatives 5 . Structure and configuration are elucidated by spectroscopic methods, and the reactivity is discussed. While compounds 5 do not react with dienophiles, the (Z)-isomers of 3 are the favored substrates for Diels-Alder reactions yielding the spiro compounds 6 and 7 .     

Hetero-Diels-Alder reaction of 3-aryl-2-benzoyl-2-propenenitriles with enol ethers. Synthesis of 2-alkoxy-3,4-dihydro-2H-pyran-5-carbonitriles

Summary The hetero-Diels-Alder reaction of 3-aryl-2-benzoyl-2-propenenitriles1a–d with enol ethers2a–c yieldscis/trans diastereoisomers of 2-alkoxy-4,6-diaryl-3,4-dihydro-2H-pyran-5-carbonitriles3 and4 in 79–98% yield. The similar reaction of1a–c with cyclic enol ether5 affords diastereoisomeric cycloadducts6 and7 withcis annulated pyran rings. Reaction of3 with sulfuric acid leads to 2-hydroxy-3,4-dihydro-2H-pyran-5-carbonitriles8 and9.

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Hetero-Diels-Alder-Reaktion von 3-Aryl-2-benzoyl-2-propennitrilen mit Enolethern. Synthese von 2-Alkoxy-3,4-dihydro-2H-pyran-5-nitrilen

Zusammenfassung Die Hetero-Diels-Alder-Reaktion der 3-Aryl-2-benzoyl-2-propennitrile1a–d mit den Enolethern2a–c ergibt diecis/trans-diastereomeren 2-Alkoxy-4,6-diaryl-3,4-dihydro-2H-pyran-5-nitrile3 und4 in einer Ausbeute von 79–98%. Dieselbe Reaktion von1a–c mit dem cyclischen Enolether5 liefert die diastereomeren Cycloaddukte6 und7 mitcis-anellierten Pyranringen. Reaktion von3 mit Schwefelsäure führt zu den 2-Hydroxy-3,4-dihydro-2H-pyran-5-nitrilen8 und9.

     

Thermische Cyclodehydratisierung von Salicylalkoholen; eine einfache Synthese von 4-substituierten 2H-Chromenen

Heating of 1-(o-hydroxyaryl)-2-propen-1-ols ( 9–13 ; see scheme 1) in diglyme solution at 147° leads to a 1,4-elimination of water to yield ω-vinyl-o-quinomethides ( b ; see scheme 2) as intermediates which cyclise rapidly to form 2H-chromenes ( 17–21 ). 1-(o-Hydroxyphenyl)-5-hexen-1-ol ( 14 ) on heating at 147° is transformed into o-(1,5-hexadienyl)-phenol ( 23 ). This phenol rearranges at higher temperature (270°) in N,N-diethylaniline to yield a mixture of 2,4-propanochromane ( 25 ) and cis- and trans-3,4-propanochromane (cis- and trans- 26 ). The kinetically controlled ratio of these compounds is 2,8:1:2,9. The formation of 25 and 26 can be explained by an intramolecular Diels-Alder reaction (see scheme 3).     

Hetero-<Emphasis Type="Italic">Diels-Alder</Emphasis> reaction of propenenitriles with enol ethers: a convenient approach to functionalized 3,4-dihydro-2<Emphasis Type="Italic">H</Emphasis>-pyrans

The hetero-Diels-Alder reaction of 3-(N-acetyl-N-benzylamino)-2-formylprop-2-enenitrile with enol ethers yielded cis/trans diastereoisomers of 2-alkoxy-4-amino-3,4-dihydro-2H-pyran-5-carbonitriles in moderate yields. Acidic hydrolysis of cis-diastereoisomer in concentrated sulfuric acid gave 2-oxo-1,2-dihydropyrydine-3-carbaldehyde. The reaction of 2-benzoyl-3-heteroaromaticprop-2-enenitriles with enol ethers afforded diastereoisomeric cis/trans cycloadducts in good yields. The structure of the products is discussed in terms of configuration and preferred conformation. Correspondence: Aleksandra Pałasz, Department of Organic Chemistry, Jagiellonian University, Kraków, Poland.     

Zur Reaktion vonE/Z-N-Benzolsulfonyl-3(2-methoxyvinyl)-indol mit Carbo- und Heterodienophilen: NeueDiels-Alder-Addukte aus der Indol- bzw. Carbazol-Reihe,V

E/Z-Benzenesulfonyl-3(2-methoxyvinyl)-indole1 reacts viaDiels-Alder type mechanism with dimethyl acetylendicarboxylate, N-phenyltriazolindione and diethyl mesoxalate to give new cycloadducts2–5 with [b]annellated indole structures.

     

Synthesis of a Fullerene Derivative of Benzo[18]crown-6 by Diels-Alder Reaction: Complexation Ability,Amphiphilic Properties,and X-Ray Crystal Structure of a Dimethoxy-1,9-(methano[1,2]benzenomethano)fullerene[60] Benzene Clathrate

A fullerene derivative 1 of benzo[18]crown-6 was obtained by Diels-Alder addition of fullerene[60](C₆₀) to the ortho-quinodimethane prepared in situ from 4,5-bis(bromomethyl)benzo[18]crown-6 ( 3 ) with Bu₄NI in toluene. Extraction experiments show that the complexation of K⁺ ions strongly increases the solubility of 1 in protic solvents like MeOH. Using Langmuir-Blodgett techniques, monolayers of the highly amphiphilic fullerene-derived crown ether 1 and its K⁺ ion complex were prepared. An X-ray crystal structure was obtained from a benzene clathrate of comparison compound 2 , synthesized by Diels-Alder reaction of C₆₀ with the ortho-quinodimethane derived from 1,2-bis(bromomethyl)-4,5-dimethoxybenzene ( 4 ). Both the fullerene molecule 2 and the benzene molecule are fully ordered in a crystal packing which is stabilized by intermolecular van-der-Waals contacts between the benzene ring and the C-spheres, intermolecular C…?C contacts between the C₆₀ moieties, and intermolecular O…?C contacts between the O-atoms of the veratrole moieties and fullerene C-atoms.     

Chemo- and Stereoselective Coordination of 5,6-Dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene by d8- and d6-Metal Carbonyls. Diels-Alder reactivity of Dienes Perturbed by Remote Olefin Complexation

The endocyclic double bond C(2), C(3) in 5,6-dimethylidene-7-oxabicyclo[2.2.1]-hept-2-ene ( 1 ) can he coordinated selectively on its exo-face before complexation of the exocyclic s-cis-butadiene moiety. Irradiation of Ru₃(CO)₁₂ or Os₃(CO)₁₂ in the presence of 1 gave tetracarbonyl [(1R,2R, 3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo[2.2.1]-hept-2-ene)]ruthenium ( 6 ) or -osmium ( 8 ). Similarly, irradiation of Cr(CO)₆ or W(CO)₆ in the presence of 1 gave pentacarbonyl[(1R, 2R, 3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene)]chromium (10) or -tungsten (11) . Irradiation of complexes 6 and 11 in the presence of 1 led to further CO substitution giving bed-tricarbonyl-ae-bis[(1R,2R,3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene)]ruthenium ( 7 ) and trans-tetracarbonyl[(1R,2R,3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo-[2.2.1]hept-2-ene)]tungsten (12) , respectively. The diosmacyclobutane derivative cis-m?-[(1R,3R,3S,4S)-(5,6-dimethylidene-7-oxabicyclo[2.2.1]hepta-2,3-diyl)]bis(tetracarbonyl-osmium) (Os-Os) (9) wa also obtained. The Diels-Alder reactivity of the exocyclic s-cis-butadiene moiety in complexs 7 and 8 was found to be significantly higher than that of the free triene 1 .