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Cyclobutanone ring

The ring opening of certain fused ring cyclobutanones led to the preparation of larger ring system. It was reported 801 that the electrophilic addition of trimethyl-silyl iodide in the presence of catalyst promoted the ring opening of (238) (240) and (242) to afford (239), (241) and (243) respectivly 80). [Pg.119]

Cyclobutanones and Cyclobutenones.—Compound (185) has been made by routine methods from precursors which already contain the four-membered ring. Cyclobutanone itself may be obtained by solvolysis of 1-cyclobutenyl nonafluorobutanesulphonate. Interestingly, the rate of this solvolysis in buffered aqueous ethanol is much faster than that of cyclopentenyl and cyclo-hexenyl homologues. It compares with the rate of solvolysis of the cyclo-octenyl compound which can react via a linear, vinylic, cationic intermediate. The rate enhancement of the four-membered vinylic compound is almost certainly due to the intermediacy of the delocalized ion (186), a species which was implicated... [Pg.57]

When an aryl substituent is placed at C-5 of a 4-substituted cyclohexenone, a new product type containing a cyclobutanone ring is formed. [Pg.786]

There is some spectral evidence that acylation of enamines of cyclic ketones with acid chlorides having an a-hydrogen in the presence of triethylamine proceeds via the ketene and subsequent cycloaddition (84). The intermediate cyclobutanone is then opened to give the enamino ketone which is hydrolyzed to the 2-acyl cyclohexanone. In the case of enamines of larger cyclic ketones the alternate mode of the cyclobutanone opening predominates, with the formation of ring-expanded 1,3-diketones upon... [Pg.139]

Though the reaction is not general, certain cyclic ketones can be photolyzed to give ring-contracted products.In the example above, the cyclobutanone (55) was photolyzed to give (56), where BZ is benzoyl. This reaction was used to synthesize tetra-r rf-butyltetrahedrane (57). [Pg.1354]

A series of 2-vinyl-3-silyloxybicyclo[3.2.0]heptan-6-ones has also been converted to prostanoid lactones in excellent yield but variable regioselectivity. Some of the best regioselectivity was obtained using H202 in trifluoroethanol (see p. 1097).241 The strained cyclobutanone ring and the relatively unreactive terminal vinyl group favor the desired reaction in preference to alkene epoxidation. [Pg.1138]

The ambivalent aptitude of sulfur [19] to stabilize adjacent anionic as well as cationic centers is a remarkable fact that has shown to be a reliable feature for the assembly of four-membered ring scaffolds utilizing cyclopropyl phenyl sulfides [20]. Witulski and coworkers treated the sulfide 1-69 with TsOH in wet benzene (Scheme 1.19) [21]. However, in addition to the expected cyclobutanone derivative 1-70, the bicyclo[3.2.0]heptane 1-70 was also obtained as a single diastereoisomer, but in moderate yield. Much better yields of 1-71 were obtained using ketone 1-72... [Pg.21]

This chapter begins by classifying the combinations of oxidation/reduction processes with subsequent cationic transformations, though to date the details of only two examples have been published. The first example comprises an asymmetric epoxidation/ring expansion domino process of aryl-substituted cyclopropyl-idenes (e. g., 7-1) to provide chiral cyclobutanones 7-3 via 7-2, which was first described by Fukumoto and coworkers (Scheme 7.1) [2]. [Pg.494]

The same epoxide 335 was easily obtained in mild conditions (0°C, 5 min) by m-ehloroperbenzoic acid oxidation [13b]. Epoxidation of alkylidenecyclo-propanes by m-chloroperbenzoie acid has been greatly exploited as a route to the synthesis of cyclobutanones 638 via the well known ring expansion of oxaspiropentanes 637 (Scheme 98) [176,177,8]. [Pg.98]

CsF induces the ring-opening cyclization of the thus obtained l-[2-(trimethylsilylmethyl)cyclopropylcarbonyl] imidazole 154 with diethyl fumar-ate or diethyl maleate to give the cyclobutanone 155 [80], The facile ring fission of 154 also occurs in the presence of BF3OEt with the formation of the corresponding y,<5-unsaturated carboxylic acid. (Scheme 55)... [Pg.131]

Addition of alkyllithium to cyclobutanones and transmetallation with VO(OEt)Cl2 is considered to give a similar alkoxide intermediates, which are converted to either the y-chloroketones 239 or the olefinic ketone 240 depending on the substituent of cyclobutanones. Deprotonation of the cationic species, formed by further oxidation of the radical intermediate, leads to 240. The oxovanadium compound also induces tandem nucleophilic addition of silyl enol ethers and oxidative ring-opening transformation to produce 6-chloro-l,3-diketones and 2-tetrahydrofurylidene ketones. (Scheme 95)... [Pg.147]

Cyclobutanon-Ring in 2,3-Stellung einem gcsattigten 6- oder 8-gliedri-... [Pg.188]

In the oxygen analogue, the enone itself is sufficiently electrophilic that attempted hydrolysis of the THP ether in enone 55 only produces the ring expanded cyclobutanone (eq. 54)96). The overall result of this sequence for electrophilic partners constitutes a 2-oxocyclobutylation alpha to a carbonyl group (see Eq. 53). [Pg.47]

A bis-vinylogue of a cyclopropylcarbinol 57 arises by standard transformations (Eq. 59) from the Peterson olefination product 56. Here too, acid induced rearrangement proceeds exclusively to the cyclobutanone and not to larger ring products93). [Pg.48]

Whereas lactone annulation invokes a relief of strain of the four membered ring by migration of the ring bond to an electron deficient oxygen, a similar migration to an election deficient carbon creates a cyclopentanone synthesis (Eq. 73). The release of approximately 84 kJ/mole (20 kcal/mole) provides a strong driving force. Thus, the 1,1-cyclobutanone annulation of ketones translates into a 1,1-cyclopentanone annulation. [Pg.51]

Placing the electron deficient migration terminus within the original carbonyl partner converts the 1,1-cyclobutanone annulation into a 1,2- or lateral cyclo-pentenone annulation as summarized in Eq. 77. In the ring enlargement of 65 to 66,... [Pg.52]

Treatment of the adducts of 30 and ketones with excess HC1 in the presence of a Lewis acid leads directly to an acyclic system as in 85 (Eq. 105) 122). It is likely that the thiophenol liberated in the ring expansion to the cyclobutanone 86... [Pg.60]


See other pages where Cyclobutanone ring is mentioned: [Pg.408]    [Pg.115]    [Pg.833]    [Pg.408]    [Pg.115]    [Pg.833]    [Pg.194]    [Pg.77]    [Pg.79]    [Pg.159]    [Pg.128]    [Pg.471]    [Pg.137]    [Pg.228]    [Pg.455]    [Pg.455]    [Pg.459]    [Pg.306]    [Pg.168]    [Pg.174]    [Pg.175]    [Pg.191]    [Pg.328]    [Pg.328]    [Pg.80]    [Pg.194]    [Pg.247]    [Pg.146]    [Pg.94]    [Pg.187]    [Pg.188]    [Pg.188]    [Pg.14]    [Pg.9]    [Pg.12]    [Pg.29]    [Pg.59]   
See also in sourсe #XX -- [ Pg.238 ]




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Cyclobutanone

Cyclobutanone ring 7-lactones

Cyclobutanone-ring expansion

Cyclobutanones

Cyclobutanones ring expansion

Cyclobutanones via ring expansion

Cyclobutanones, 2-vinyldivinyl ketones from via ring expansion of cyclopropylcarbinols

Sulfoxide, methyl 2-chlorophenyl ring expansion with cyclobutanones

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