The Thermal Isomerizations of Bicyclo[2.1.0]pent‐5‐yl Methyl Ketones: <i>endo‐exo</i> stereomutation and cyclopropyl‐allylic rearrangement to cyclopent‐2‐enyl methyl ketones

Grosclaude, Jean-Pierre; Gonzenbach, Hans-Ulrich; Perlberger, Jean-Claude; Schaffner, Kurt

doi:10.1002/hlca.19760590830

Cited by 6 publications

(2 citation statements)

References 18 publications

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“…The formation of the thermally labile [34] oxadi-n-methane-rearrangement products on direct irradiation, which remained below reliable detection limits in the first photochemical study of Ib [3], has now been demonstrated by the use of improved analytical conditions. Figure 3.…”

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Photo‐CIDNP. Investigation of β,γ‐Unsaturated Ketones: Evidence for Temperature‐dependent S₁vs. T₂ Reactivities of Cyclopent‐2‐enyl Methyl Ketones

Henne¹,

Siew²,

Schaffner³

1979

Helvetica Chimica Acta

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On ultraviolet irradiation of the cyclopent-Zenyl methyl1 ketones la-c at -5 4 " s t I 139", photo-CIDNP. effects of the starting ketones, the 1,3-acetyl shifted isomers (2), and radical disproportionation and corn bination products (4-7) were observed. These effects show a unique dependence (of the polarization phase on temperature which is a novel feature in photo-CIDNP. studies. The results of the investigation, which also included experiments using triplet quenchers, triplet sensitizers and radical scavengers, are ratilonalized in terms of Schemes 2 and 3.a-Cleavage is a major excited-state reaction of 1 a-c on direct irradiation.Temperature-activated a-cleavage (k:(t)) to the radical pair R . . R" and intersystem crossing (&) to the T, state are among the competing s, deactivation processes. The T, state in turn cleaves (kz2) to R.-R'3. A 'low-temperature range' with k& k,S ( t ) and a 'high-temperature range' with k,S ( t ) % kisc exhibiting preferential reactivity from the T, and S 1 states, respectively, can be defined for all three p , y-unsaturated ketones la-c.Introduction. -Most 8, y-unsaturated ketones predominantly undergo two characteristic photoreactions: an allylic 1,3-acyl shift on direct irradiation, and a triplet sensitized oxadi-n-methane rearrangement (Scheme These results clearly showed from the beginning that at least two excited states are reactive. It has been universally accepted that the oxadi-n-methane rearrangement occurs from the lowest-lying triplet (TJ, and that this state is predominantly 7z, n+& in nature3). The I) 2, 3, Present address: Wissenschaftliches Hauptlaboratorium WHZ, BASF AG, D-6700 Ludwigshafen. See 111 for comprehensive reviews of P,y-unsaturated ketone photochemistry, and 121 for a progress report on cyclopent-2-enyl methyl ketones. For experimental identifications of Tl(rc,rc*) as the oxadi-rc-methane-reactive state, see 13-51, 0018-019X/79/6/ 1952-14$01.00/0 0 1979 Schweizerische Chemische Gesellschaft 5b. .Y = H b , The denotations (a)-(e) refer to the signal assignments in Figure I . Cf: Figure I A . d)CJ Figure 1B. e, A=enhanced absorption, E=emission. Negligible CIDNP. effect. g) in CD30D at -54".

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confidence: 99%

Photo‐CIDNP. Investigation of β,γ‐Unsaturated Ketones: Evidence for Temperature‐dependent S₁vs. T₂ Reactivities of Cyclopent‐2‐enyl Methyl Ketones

Henne¹,

Siew²,

Schaffner³

1979

Helvetica Chimica Acta

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“…37b). A precedent for such a I rearrangement is found in the thermal rearrangement of 38 to 39 (23), which on the basis of kinetic evidence has been proposed to involve a concerted I ,2, + ,2, process analogous to that shown in 37a. In the present case the observation of the formation of only the AIB-cis isomer provides some grounds for favoring the concerted mechanism.…”

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Bridged-ring steroids. II. The synthesis of bridged steroids with a bicyclo[2.2.1]heptane ring A system

Yates¹,

Winnik²

1981

Can. J. Chem.

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PETER YATES and FRANFOISE M. WINNIK. Can. J. Chem. 59, 1641 (1981).Bridged steroids with a bicyclo[2.2.l]heptane ring A system are formed on thermolysis of 5-vinyl 3-keto steroids. 5-Vinyl-Sa-cholestan-3-one (26) on being heated at 350°C in decalin gave 2a,5-(syn-methylmethano)-Sa-cholestan-3-one (27). Similar treatment of 17~-hydroxy-S-vinyl-S~-estran-3-one (21) gave 17P-hydroxy-2P,5-(syn-methylmethano)-SP-estran-3-one (M), which was also obtained by reduction of 2P,S-(syn-methylmethano)-SP-estrane-3,17-dione (31) with sodium borohydride on alumina. Compound 31 was formed as the major product on thermolysis of 5-vinyl-5P-estrane-3,17-dione (24) at 350°C, together with 5-(trans-propeny1)-A-nor-SP-estrane-3,17-dione (32). Compounds 27, 30, and 31 are considered to arise via intramolecular ene reactions of the A*-enols of compounds 26, 21, and 24, respectively. Compound 32 is postulated to be formed via an analogous reaction of the A3-enol of 24, followed by thermolysis of the resulting 3'-methyl-4~,5-dihydrocyclopropa[4,5]-5~-estrane-3,17-dione (36). Photolysis of 30 in methanol results in a-cleavage of the C2-C3 bond and the formation of a ketene-derived ester and two enal-derived oxetanes.PETER YATES et FRAN~OISE M. WINNIK. Can. J. Chem. 59, 1641 (1981). La thermolyse des vinyl-5 ceto-3 stero~des conduit a la formation de stero~des pontes portant au niveau du cycle A un bicyclo[2.2.1] heptane. Si on chauffe la vinyl-5 5a-cholestanone-3 (26) dans de la decaline a 350"C, on obtient la (methylmCthano syn)-2a,5 5a-cholestanone-3 (27). L'hydroxy-17P vinyl-5 SP-estranone-3 (211, traitee de la mime f a~o n , fournit I'hydroxy-17P (methylmethano syn)-2P,5 SP-estranone-3 (30) que I'on obtient egalement par reduction de la (methylmethano syn)-2P,S SP-estraned~one-3,17 (31) par le borohydrure de sodium sur I'alumine. Le composk 31 se forme comme le produ~t principal de la thermolyse de la Bridged steroids are of interest both because of their potential biological activity and because they can serve as substrates for the study of the effects of the constraints imposed on bridged bicyclic systems by the steroid skeleton in the course of the I reactions of such systems.We and others have previously investigated the synthesis of steroids incorporating a bicyclo-[2.2.2]octane (2, and references therein quoted) or bicyclo[3.2. ]]octane system (3). Here we are concerned with the incorporation of a bicyclo-[2.2.l]heptane system. Solo et al. have made extensive investigations of bridged ring D steroids of this type, which they synthesized by Diels-Alder addition of dienophiles to steroid 14,16-dienes (4, and earlier papers in this series). However, the only previous work to our knowledge that led to the incorporation of a bicyclo[2.2. llheptane system into a steroid ring other than ring D is that of Nazer ( 9 , who obtained compounds la and l b by treatment of 2a and 2b, respectively, with lithium (3), C2 and C5 (4), or C3 and C10 (5) (the last being possible only in the 19-nor series). Our initial approach was to a system of typ...

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ChemInform Abstract: THE THERMAL ISOMERIZATIONS OF BICYCLO(2.1.0)PENT‐5‐YL METHYL KETONES‐ ENDO‐EXO STEREOMUTATION AND CYCLOPROPYLALLYLIC REARRANGEMENT TO CYCLOPENT‐2‐ENYL METHYL KETONES

Grosclaude¹,

Gonzenbach²,

Perlberger³

et al. 1977

Chemischer Informationsdienst

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The Thermal Isomerizations of Bicyclo[2.1.0]pent‐5‐yl Methyl Ketones: endo‐exo stereomutation and cyclopropyl‐allylic rearrangement to cyclopent‐2‐enyl methyl ketones

Cited by 6 publications

References 18 publications

Photo‐CIDNP. Investigation of β,γ‐Unsaturated Ketones: Evidence for Temperature‐dependent S₁vs. T₂ Reactivities of Cyclopent‐2‐enyl Methyl Ketones

Photo‐CIDNP. Investigation of β,γ‐Unsaturated Ketones: Evidence for Temperature‐dependent S₁vs. T₂ Reactivities of Cyclopent‐2‐enyl Methyl Ketones

Bridged-ring steroids. II. The synthesis of bridged steroids with a bicyclo[2.2.1]heptane ring A system

ChemInform Abstract: THE THERMAL ISOMERIZATIONS OF BICYCLO(2.1.0)PENT‐5‐YL METHYL KETONES‐ ENDO‐EXO STEREOMUTATION AND CYCLOPROPYLALLYLIC REARRANGEMENT TO CYCLOPENT‐2‐ENYL METHYL KETONES

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The Thermal Isomerizations of Bicyclo[2.1.0]pent‐5‐yl Methyl Ketones: endo‐exo stereomutation and cyclopropyl‐allylic rearrangement to cyclopent‐2‐enyl methyl ketones

Cited by 6 publications

References 18 publications

Photo‐CIDNP. Investigation of β,γ‐Unsaturated Ketones: Evidence for Temperature‐dependent S1vs. T2 Reactivities of Cyclopent‐2‐enyl Methyl Ketones

Photo‐CIDNP. Investigation of β,γ‐Unsaturated Ketones: Evidence for Temperature‐dependent S1vs. T2 Reactivities of Cyclopent‐2‐enyl Methyl Ketones

Bridged-ring steroids. II. The synthesis of bridged steroids with a bicyclo[2.2.1]heptane ring A system

ChemInform Abstract: THE THERMAL ISOMERIZATIONS OF BICYCLO(2.1.0)PENT‐5‐YL METHYL KETONES‐ ENDO‐EXO STEREOMUTATION AND CYCLOPROPYLALLYLIC REARRANGEMENT TO CYCLOPENT‐2‐ENYL METHYL KETONES

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Photo‐CIDNP. Investigation of β,γ‐Unsaturated Ketones: Evidence for Temperature‐dependent S₁vs. T₂ Reactivities of Cyclopent‐2‐enyl Methyl Ketones

Photo‐CIDNP. Investigation of β,γ‐Unsaturated Ketones: Evidence for Temperature‐dependent S₁vs. T₂ Reactivities of Cyclopent‐2‐enyl Methyl Ketones