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].     

Photoisomerisierung von o-Di-isobutenylbenzol

o-Di-isobutenyl-benzene ( 4 ) on irradiation in hexane with a low-pressure mercury lamp gives 4 photoproducts in an overall yield of 24%. Three of these products were identified as 4, 4, 6, 6-tetramethyl-benzobicyclo [3.1.0] hex-2-ene ( 5 , main product, 14%), 1.1-dimethyl-2-isopropenyl-indane ( 6 , 8%) and 1-isopropenyl-2, 2-dimethyl-indane ( 10 , 2%). 6 is also formed by irradiation of 5 in hexane.     

Zur Photodimerisierung von 3-Phenyl-2H-azirinen. Vorläufige Mitteilung

Irradiation of 3-phenyl-2H-azirine ( 2 ) in benzene solution with a high-pressure mercury lamp yields 4,5-diphenyl-1,3-diazabicyclo[3,1,0]hex-3-ene ( 4 ) and not 3-phenylimino-4-phenyl-1-azabicyclo[2,1,0]pentane ( 1 ), as had been reported previously by others [2]. 2-Methyl-3-phenyl-2H-azirine ( 3 ) yields on irradiation a 2:1 mixture of 2-exo, 6-exo- and 2-exdo, 6-exo-dimethyl-4,5-diphenyl-1,3-diazabicyclo[3,1,0]hex-3-ene (2-exo,6-exo- and 2-endo, 6-exo- 5 ). Irradiation of 2,3-diphenyl-2H-azirine ( 8 ) leads to the formation of 2,4,5-triphenyl-imidazole ( 9 ) and tetra-phenylpyrazine ( 10 ). The suggested reaction path for the generation of 9 and 10 is shown in Scheme 2.     

Aromatische [1,5s]-sigmatropische H-Verschiebungen in Arylallenen

1-Mesityl allene ( 1 ), 1-mesityl-3-methyl allene ( 2 ) and 1-mesityl-3,3-dimethyl allene ( 3 ) rearrange thermally at 150–190° in decane via [1,5s]sigmatropic H-shifts to yield the o-quinodimethanes 4 , which cyclise to give the 1,2-dihydronaphthalenes 5 and 6 and/or undergo [1,7 a]sigmatropic H-shifts to give 1-mesityl-(Z)-buta-1, 3-dienes (Z)- 7 and (Z)- 8 , respectively (Schemes 1,3,4 and 5) in almost quantitative yields. The activation parameters of these isomerisations are given in Table 1. 1-Mesityl-1-methyl allene ( 9 ) isomerises at 190° to give 4,5,7-trimethyl-1,2-dihydronaphthalene ( 17 ) in 50% yield (Scheme 6). 2′-Isopropylphenyl allene ( 10 ) in decane rearranges at 170° to 1-(Z)-propenyl-2-isopropenyl-benzene ((Z)- 19 , Scheme 7). Deuterium labelling experiments show that the rate determining step is an aromatic [1,5s]sigmatropic hydrogen shift from an sp³- to an sp-hybridised carbon atom. The primary kinetic isotopic effect (k_H/k_D) is 3.45, while the secondary βisotopic effect is 1.20 (Scheme 7 and Table 2).     

Photochemie von 1,1-Dimethyl-4-phenyl- und 1-Methyl-1-phenyl-1,2-dihydronaphthalin; Nachweis einer photochemischen,sigmatropischen [1,7]H-Verschiebung. 41. Mitteilung über Photoreaktionen

Photochemistry of 1,1-dimethyl-4-phenyl-and 1-Methyl-1-phenyl-1,2-dihydronaphthalene; evidence for a photochemical, sigmatropic [1,7]H-shift. Irradiation of 1,1-dimethyl-4-phenyl-1,2-dihydronaphthalene ( 11 ) and 1-methyl-1-phenyl-1,2-dihydronaphthalene ( 8 ) in pentane were investigated at ?112° to ?118°, using a mercury high pressure lamp. The [1,5]-hydrogen-shift products 13 and 17 , respectively, the [1,7]-hydrogen-shift products 15 and 10 , respectively and the photochemical Diels-Alder products 14 and 18 , respectively, were obtained, presumably via the ω-vinyl-o-quinodimethane intermediates 12 and 9 (Schema 3). Irradiation of the 1,2-dihydronaphthalene 11 at ?181° to ?183° in a 2,2-dimethylbutane/pentane matrix, gave rise to an UV.-maximum at 402 nm which is assigned to the o-quinodimethane derivative 12 . After warming the solution around ?130° or to room temperature, a product mixture was obtained, which mainly consist of the [1,7]-hydrogen-shift product 15 accompanied by the [1,5]-hydrogen-shift products 13 and 16 and the photochemical Diels-Alder product 14 (Table 1). When the o-quinodimethane intermediate 12 was irradiated with 406 nm-light, the longwavelength absorption completely disappeared. This solution, after warmingup, yielded mainly the [1,5]-hydrogen-shift products 13 and 16 together with the bicyclic compound 14 and surprisingly a small amount of the [1,7]-hydrogen-shift product 15 (Table 1). Similar experiments were carried out with the 1,2-dihydronaphthalene 8 . The results clearly indicate that irradiation of the o-quinodimethane 9 at ?180° to ?185° with 406 nm-light caused [1,5]- and [1,7]-hydrogen shifts in a ratio of approximately 1:1 (Table 2). From the experiments described above it follows, that the phenyl-substituted α-methyl-ω-vinyl-o-quinodimethanes 12 and 9 undergo upon irradiation with light of λ > 400 nm, besides photochemical Diels-Alder reactions, also [1,5]- and [1,7]- hydrogen shifts. It is remarkable that the thermal [1,7]-hydrogen-shifts of the o-quinodimethanes 12 and 9 occur readily around ?130°, whilst a temperature of ?70° is needed to promote [1,7]-hydrogen-shifts in the non-phenylated o-quinodimethanes of the type 2 (Schema 1). The phenyl group in ω- or α-position may enter into conjugation with the π-system in the helcal transition state of the [1,7]-hydrogen shift, but not in the reactants 12 and 9 .     

The Reaction of Dihalocarbenes with Quadricyclane

The reactions of difluoro-, dichloro- and dibromocarbene with quadricyclane ( 2 ) were examined. In all cases, conversions were low (4–15%), but three distinct reaction courses were observed: cleavage, 1,2-addition, and 1,4-addition. Difluorocarbene gave mainly 6-endo-(2,2-difluorovinyl)-cis-bicyclo[3.1.0]hex-2-ene ( 8 ; 52–89% relative yield), together with minor amounts of exo-3,3-difluorotricyclo[3.2.1.0^2,4]oct-6-ene (7; 13–17%), and 4,4-difluorotetracyclo[3.3.0.0^2,8.0^3,6]octane ( 5 ; 2–4%). Dichlorocarbene gave analogous products, but in relative yields of 35 ( 17 ), 51 ( 11 ), and 12% ( 16 ). The product 11 of 1,2-endo addition underwent further rearrangement to its allylic derivative 12 . A small amount of 1,2-endo addition also occurred (2% of 14 / 15 ). Dibromocarbene gave predominantly products derived from rearrangement of the 1,2-exo (61% of 20 / 21 ) and 1,2-endo adducts (10% of 23 / 24 ). In addition, a significant amount of 4,4-dibromotetracyclo[3.3.0.0^2,8.0^3,6]octane ( 25 ; 21%) was formed. The cleavage product, 6-endo-(2,2-dibromovinyl)-cis-bicyclo[3.1.0]hex-2-ene ( 26 ) was also observed (7%). The yields and product compositions were compared to those obtained from norbornadiene ( 1 ) and found to be entirely different (Table 1), for example no cleavage occurred with difluorocarbene.     

Thermal decomposition products of methyl 1,5-diphenyl- and 5-methyl-1-phenyl-2,3-diazabicyclo[3.1.0]hex-2-ene-6-exo-carboxylates

Methyl 1,5-diphenyl- and 5-methyl-1-phenyl-2,3-diazabicyclo[3.1.0]hex-2-ene-6-exo-carboxylates at 138°C undergo decomposition via elimination of nitrogen molecule with formation in each case of five products. Two products are methyl 1,3-diphenyl(or 1-methyl-3-phenyl)bicyclo[1.1.0]butane-2-endo- and -exo-carboxylates, and the three others are derivatives of buta-1,3-diene, methyl (Z)-2-benzylidene-3-phenyl(or 3-methyl)but-3-enoate and methyl (E)- and (Z)-3,4-diphenyl(or 4-methyl-3-phenyl)penta-2,4-dienoates. The formation of these products may be rationalized assuming intermediacy of substituted allylcarbene which undergoes both intramolecular cycloaddition and rearrangements involving 1,2-hydride and 1,2-vinyl shifts.     

Sigmatropic Rearrangements Accompanying the Addition of Dichlorocarbene to Norbornadiene

A new product arising from the reaction of dichlorocarbene with norbornadiene, 6endo-(2,2-dichlorovinyl)-cis-bicyclo[3.1.0]hex-2-ene, is described. It does not arise from the normal exo-l,2-adduct, but possibly originates by sigmatropic rearrangement of an initially formed zwitterionic intermediate.     

Reaction of difluorocarbene with 2H-azirines: generation and transformations of strained azomethine ylides -- aziriniodifluoromethanides

The reaction of difluorocarbene with azirines affords a new type of azomethine ylides, viz., strained aziriniodifluoromethanides. 1,3-Dipolar cycloadditions of ylides derived from 2-unsubstituted 3-arylazirines to dimethyl acetylenedicarboxylate and aldehydes give derivatives of 2,2-difluoro-1-azabicyclo[3.1.0]hex-3-ene-3,4-dicarboxylic acids and 1,4-oxazin-3(4H)-ones, respectively. Ylides derived from 2-mono- and 2,2-disubstituted azirines undergo isomerization to 2-aza-1,3-diene derivatives. 2,2-Difluoro-1-azabicyclo[3.1.0]hex-3-enes are transformed into 2-fluoropyridine derivatives in high yields and react with amines to give 2,4-diamino-1-azabicyclo[3.1.0]hex-2-ene derivatives.     

13C-NMR-spektren von bicyclo[n.1.0]alkenen

The ¹³C-NMR spectra of some bicyclo[3.1.0]hex-3-en-2-ols and of some bicyclo[3.1.0]hex-3-en-2-ones are described. The bond parameters of bicyclo[3.1.0]hex-3-en-2-one are derived from a structure determination of endo-6-methoxy-1,3,6-triphenylbicyclo[3.1.0]hex-3-en-2-one. The electron density is calculated by the EHT method, and correlated with the ¹³C NMR shifts. For comparison the ¹³C NMR spectrum of a bicyclo[4.1.0]hepta-1,5-dione derivative is analysed. The influence of a cyclopropane system attached to a five-membered and to a six-membered ring is elucidated. Whereas the five-membered ring shows conjugation between the carbonyl group and the cyclopropane system, the same effect is not observed in the six-membered ring analogue. This is explained by the highly rigid structure of the five-membered ring.     

Photochemical isomerization of 2H-imidazoleN-oxides

1,3-Diaza-6-oxabicyclo[3.1.0]hex-3-enes and their 3-oxides were obtained by the photolysis of 2H-imidazole 1-oxides and 2H-imidazole 1,3-dioxides. 1,3-Diaza-6-oxabicyclo [3.1.0]hex-3-ene 3-oxides are thermally unstable and are converted to the starting 2H-imidazole 1,3-dioxides; their further photolysis affords a mixture of stereoisomeric 1,3-diaza-4,7-dioxatricyclo [4.1.0.0^3,5]heptanes.For the previous communication, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2096–2100, December, 1993.     

The photosensitized rearrangement of aryl-substituted tricyclo[2.2.0.02,6]hexanes to bicyclo[3.1.0]hex-2-enes

The triplet sensitized irradiation of 3-allyl-diaryl-substituted cyclopropenes to bicyclo[3.1.0]hex-2-enes proceeds via an intramolecular [2+2]-cycloaddition followed by a subsequent rearrangement of the initially formed tricyclo[2.2.0.0^2,6]hexane skeleton.     

Bicyclic monoterpenoids of the essential oil of Ledum palustre

The structure of a new natural compound has been established as 5-isopropylbicyclo[3.1.0]hex-3-en-2-one, which has been called lebaikon. Two bicyclic monoterpenoids (2-formyl-5-isopropylbicyclo[3.1.0]hex-2-ene and 4-isopropyl-1-methylbicyclo[3.1.0]hexan-2-one) have been detected in natural materials for the first time.     

Photochemistry of azole N-oxides. Facile photoisomerisation of 2H-imidazole N-oxides to 1,3-diaza-6-oxabicyclo[3.1.0]hex-3-enes and synthesis of a 1,3-diaza-4,7-dioxatricyclo[4.1.0.1,603,5]heptane

Ultraviolet irradiation of a series of 2H-imidazole N-oxides 2 has been shown to effect a clean isomerisation to derivatives of the new ring system, 1,3-diaza-6-oxabicyclo[3.1.0]hex-3-ene, 7 . Epoxidation of a representative 7 has given access to the hitherto inaccessible trans-fused 1,3-diaza-4,7-dioxatricyclo[4.1.0. ^1,60^3,5]-heptane ring system 9 .     

Reactions of [2+2+1]-cycloaddition with the participation of cyclopropenes and dicobalt hexacarbonyl complexes of acetylenes

The reaction of dicobalt hexacarbonyl complexes of acetylene and its phenyl and dimethyl derivatives with the methyl ester of 1-methyl-2-(trimethylsilyl)-1-cyclopropene-3-carboxylic acid with adsorption on a silica gel or NaX zeolite surface leads to the formation of a mixture of bicyclo[3.1.0]hex-2-en-4-one and tricyclo[4.1.0.0^2,4]heptan-5-one derivatives, whereby the yields and the composition of products are dependent on the type of the adsorbent. It has been found that under the reaction conditions partial isomerization of the bicyclo-[3.1.0]hex-2-en-4-one derivatives into substituted phenols occurs. Action of anhydrous KF and crown-ether in acetonitrile on the bicyclo[3.1.0]hex-2-en-4-one derivatives in acetonitrile leads to protodesilylation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2565–2571, November, 1991.     

Generation and reactivity of sterically hindered bicyclo[3.1.0]hex-1-enes

2-t-butylbicyclo[3.1.0]hex-1-ene dimerizes primarily by a [σ+ π] way, whereas 2,5-di-t-butylbicyclo[3.1.0]hex-1-ene undergoes an unusual hydrogen shift reaction to 1,3-di-t-butyl-2-methylcyclopentadiene.     

Thermal rearrangement of divinylcyclopropane systems. Preparation of functionalized,stereochemically defined bicyclic and tricyclic products containing the bicyclo[3.2.1]octane skeleton

A study involving the preparation and thermolysis of substituted 6-$\text{exo}$-(1-alkenyl)bicyclo[3.1.0]hex-2-ene systems (14, 15, 23, 29, 40) shows (a) that C-8 functionalized bicyclo[3.2.1]octa-2,6-dienes can be prepared readily $\text{via}$ this methodology (14 → 16; 15 → 17), (b) that the rearrangement reaction is stereospecific even when the 6-(1-alkenyl) group is substituted with a sterically bulky isopropyl group (23 → 24; 29 → 30), and (c) that the method can be extended to include the preparation of tricyclic systems (40 → 41).     

Bicyclic monoterpenoids of the essential oil of Ledum palustre

The structure of a new natural compound has been established as 5-isopropylbicyclo[3.1.0]hex-3-en-2-one, which has been called lebaikon. Two bicyclic monoterpenoids (2-formyl-5-isopropylbicyclo[3.1.0]hex-2-ene and 4-isopropyl-1-methylbicyclo[3.1.0]hexan-2-one) have been detected in natural materials for the first time.Tomsk State Medical Institute. Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR, Novosibirsk. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 627–629, September–October, 1990.     

An unusual example of a 1,1-cycloaddition reaction of a diazoalkane

Thermolysis of the sodium salt of E-1,4-diphenyl-3-buten-1-one N-tosylhydrazone gave rise to the corresponding diazoalkane which undergoes a subsequent 1,1-cycloaddition reaction to produce 3,6-diphenyl-1,2-diazabicyclo[3.1.0]hex-2-ene.