Bicyclo heptanones

Irradiation of the ketone (6) in argon-degassed cyclohexane brings about Norrish Type I fission. In this case decarbonylation does not result and the triplet biradical formed by the fission affords the aldehyde (7). The enol (8) is also a product of this irradiation. An aldehyde is also the principal product on irradiation of (9) in benzene. The a-fission affords the aldehyde derivative (10) in 90% yield. Analogous behaviour is observed on irradiation of bicyclo-heptanone (11) to afford an aldehyde that was a key intermediate in the synthesis of dimethyl secologanoside. ... 

The synthesis of the bicyclo heptanone synthon 21 was achieved in five steps from isovaleraldehyde. The silyloxy aldehyde synthon 22 was synthesized from the readily available isobutenol. The cycloaddition was first attempted using standard Lewis acid conditions, with either tin chloride or tin triflate however, this led to competitive elimination and the cyclic adduct was not obtained. It was later discovered that the use of the hindered catalyst MADNTfa [(ArOjaAlNTfa] resulted in the cycloaddition, afrbrding... 

Bicyclic System Case Small-Ring-Annulated Bicyclo[2.2.1]heptanones... 

In contrast to the [2-1-2]-photocycloaddition which is a widely used method to generate four-membered rings, Koreeda and Zhang used a thermal rearrangement key step to construct the tricyclic framework of kelsoene [23]. In earlier work, it was shown that upon treatment with base, y-keto-p-toluene-sulfonate rac-32 is converted to a 44/56 mixture of bicyclo[3.1.1 ]heptanone rac-33 and bicyclo[3.2.0]heptanone rac-34 (Scheme 10) [24-26]. 

In the acid-catalyzed rearrangement of bicyclo[3.1.1]heptanones, two different cations, 1 and 2, lead to two different bicycloheptanones via 1234-1243 rearrangement. The ionic process involves sequential 1,2-alkyl shifts. Substituents at C2 and C4 determine which cationic intermediate is more stable. 

The rearrangement of bicyclo[3.1.1]heptanones to bicyclo[3.2.0]heptanones was first used for the preparation of (+ )-4,7,7-trimethylbicyclo[3.2.0]hept-3-en-6-one (4) from (— )-chrysanthenone (3).4i Prolonged treatment of (—)-chrysanthenone (3) in acidic media gave ( - )-2,7,7-trimethyl-bicyclo[3.2.0]hept-2-en-6-one (5) in 1 % yield. This rearrangement is a reversible process. 

Fr, Campher in Ger, Canfora in Ital, Alcanfor in Span Kamfora in Rus) called 1.7.7-Trimethyl -bicyclo- [l.2.2] —heptanon-(2) in Beil, ... 

The three bicyclic ketones which have been studied are norcamphor (XXI), camphor (XXII), and bicyclo [3.2.0] heptanone-3 (XXIII)... 

The application of this reaction to other ring systems has shown that the yield of the bicyclic hydrocarbon decreases as the strain involved in the product increases. For example, the mercury sensitized decomposition of bicyclo [3.2.0] heptanone-3 (XXIII) leads to very little of bicyclo [2.2.0] hexane and gives more of bicyclo [2.1.1] hexane than of bicyclo [2.2.0] hexane. The reaction has been successfully applied to the synthesis of a substituted bicyclo [2.1.0] pentane (XXVIII) from a sub-... 

We thus start with the smallest and simplest systems for which we have thermochemical data, the isomeric 2- and 7-bicyclo[2.2.1]heptanones (the norbomanones, 39a and 39b). Our intuition suggests that the latter species is more strained since the increased geometric constraints of a single-carbon bridge over those for a two-carbon bridge are... 

One more method used in the last decade is the interaction of unsaturated ketones with A-tosyliminoaryliodinanes in the presence of monovalent copper complexes [42, 43, 44, 45]. A serious disadvantage of this method is low yields. For example, in the reaction of cyclohexenone 25 with compound 26 in the presence of Cu(CH3CN)4C104, the target bicyclo[4.1.0]heptanone 27 was obtained with 21% yield [42] (Scheme 1.8). 

In the optical resolution of bicyclo[2.2.1]heptanones (87a, 88-90), bicyclo[2.2.2]- octanones (91-94) and bicyclo[3.2.1]octanone (95) by complexation with various chiral host compounds, some best host-guest combinations were found. Resolutions of 88, 89, 90, and 92 were accomplished efficiently by complexation with 3 to give (+)-88 (100% ee, 33%), (-)-89 (100% ee, 16%), (+)-90 (100% ee, 60%), and (-)-92 (100% ee, 41%), respectively, in the optical and chemical yields indicated.36 However, resolutions of 93 and 95 were accomplished efficiently by complexation with 8a to give optically pure (-)-93 and (-)-95 in 56 and 48% yields, respectively. On the other hand, resolution of 94 can be accomplished only by complexation with 15c to give finally (-)-94 of 100% ee in 31% yield.36 Mechanism of these chiral recognition in the inclusion complex crystal has been studied by X-ray analysis.36 Nevertheless, none of 3,8a and 15c is applicable to the resolution... 

Toda, F., Tanaka, K., Marks, D., and Goldberg, I. (1991) Optical Resolution of Bicyclo[2.2.1]heptanone, Bicyclo[2.2.2]octanone, and Bicyclo[3.2.1]octanone Derivatives by Inclusion Complexation with Optically Active Host Compounds, J. Org. Chem., 56, 7332-7335. 

Cyclopentenones undergo a clean [2 + 2]-photocycloaddition to a variety of alkenes, resulting in products with a bicyclo[3.2.0]heptanone skeleton. The two annelated... 

A stereoselective synthesis of 3-( 1,2,4-triazolo[4,3-A ]azin-3-yl)-bicyclo[2.2.1 ]heptanones 58 starting from (l/ )-(+)camphor 56 has been described. The reaction comprises oxidative cyclization of the intermediate hydrazones 57 with methanolic bromine <02TA821>. 

Hydroxide-catalysed H—D exchange at C(3) of bicyclo[2.2.1]heptanones has been the subject of intensive studies during recent years, mainly because of the peculiar observation (Thomas and Willhalm, 1965) that deuterium exchange at the exo position of isofenchone 1301 and camphor 131) is highly... 

It must be emphasized that reduction of carbonyl compounds by dissolving metals, either in the presence or absence of an added proton donor is a kinetically controlled process. This was tacitly stated in 1972," and has been repeated or implied in more recent reviews of this topic. A recent study of the reduction of several bicyclo[2.2.1]heptanones using alkali metal-NH3-NH4Cl systems emphasizes that these reductions are kinetically controlled. ... 

The dissolving metal reductions of bicyclo[2.2. l]heptanones have been studied extensively, and it has been established that both metal-alcohol and metal-NH -proton donor systems provide the cndr>-alcohol regardless of its stability relative to the exo isomer. " - In the case of camphor (1) which has been studied in the most detail, the ratio of endo-alcohol (bomeol 2) to CAo-alcohoI (isobomeol 3) is very close to 90 10 for all metal-NH3 conditions employed. The variables include temperature (-33 and -78 °C), cosolvent (ether and THF), metal (Li, Na, K, Rb) and proton donor (NH4CI and ethanol). - The same results are obtained with both (+)- and (+)-camphor. These results are, coincidentally, almost identical to the equilibrium ratio for alcohols (2) and (3). ... 

Table 1 Metal-Ammonia Reductions of Bicyclo[2.2.1]heptanones and Equilibrium Ratios of the Corresponding...

Metal-ammonia reduction of bicyclo[2,2,l]heptanones has been examined by Coulombeau and Rassat, who point out that the conformationally more stable forms of substituted alcohols are the exo-isomers in the case of norbornan-2-ol and the 1-methyl homologue, but the endo-isomers in the case of borneol (1,7,7-trimethyl) and fenchol (1,3,3-trimethyl). The same authors have also examined the reduction of camphorquinone [2,3-dioxo-bornane, (249)] with... 

Photochemical extrusion of nitrogen from the dimethylpyrazole (538) affords the substituted bicyclo[4,l,0]heptanone (539), which then suffers photo-decarb-onylation, probably via the cyclopropanone (540), to give a 1 a-isopropenyl-A-nor-2 ene (541). 

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