Cyclobutyl

Crotyl, see 2-Butenyl Cumenyl o-, m-, orp-) Cyanato Cyano Cyclobutyl Cycloheptyl Cyclohexadienyl (2,4-shown)... 

Cyclobutyl Carbamate (Chart 8). The half-life for cleavage in neat CF3CO2H is > 300 min. 

The C4H7+ cation shown as the first entry in Scheme 5.5 is a particularly interesting example. It is a bridged ion which can be reached from isomeric cyclopropylmethyl and cyclobutyl irms. 

Intramolecular hydrogen-atom abstraction is also an important process for acyclic a,/ -unsaturated ketones. The intermediate diradical then cyclizes to give the enol of a cyclobutyl ketone. Among the by-products of such photolyses are cyclobutanols resulting from alternative modes of cyclization of the diradical intermediate ... 

Phenylmercury halides give the corresponding phenylmercury derivative, CgH5HgC(CF3)3 (61%) [156], and perfluorocyclobutene gives the corresponding cyclobutyl derivative [156], Mechanistically, the reaction could be interpreted as formation of the fluorocarbanion via nucleophilic addition of fluoride ion to the fluoroolefin followed by capture of the intermediate fluorocarbanion by the mercury salt [156]. The regiochemistry of the reaction is consistent with this mechanism [156] (equation 119). 

S-Benzyl Thiocarbamate, 548 Butynyl, 548 p-Cyanobenzyl, 548 Cyclobutyl, 548 Cyclohexyl, 548 Cyclopentyl, 548 Cyclop ropy I methyl, 548 p-Decyloxybenzyl, 548 Diisopropylmethyl, 548 2,2-Dimethoxycarbonylvinyl, 548... 

R= cyclohexyl cyclopentyl cyclobutyl cyclopropyl isoamyl Me Et isopropyl... 

Butaprost (82) not only has the typical C-15 hydroxyl of the natural prostaglandins moved to C-16, as do several of the analogues discussed above, but it has a rather interesting gem dialkyl substitution at C-17, presumably for metabolic protection, in the form of a cyclobutyl ring. It is a bronchodilator and is prepared in a manner analogous to that of rioprostil discussed above [17]. 

M-Cyclobutyl methyl-14-hydroxy-3-methoxymorphinan Hydrogen Bromide... 

A1( -octalone, 45, 80 N-nitioso-N-phenylglycine to N-phenylsydnone, 45, 96 Cyclobutanecarboxylic acid, reaction with hydrazoic acid, 47, 28 Cyclobutene, 1,2,3,4-tetrasiethyl-3,-4-dichloro-, 46, 34 reactions of, 46, 36 Cyclobutylamine, 47, 28 Cyclobutyl isocyanide, 46, 77 Cycloheptanone, 45, 31... 

The key features of Pirrung s synthesis of isocomene are outlined retrosynthetically in Scheme 1. Working one step back from 1 gives the tertiary carbocation intermediate 2. The intermediacy of 2 should be brief, for it should readily participate in an Ei-type reaction, in the forward sense, to give isocomene (1). Inspired by the observation that bicyclo[3.3.0] frameworks can be accessed from bicyclo[4.2.0] frameworks through cyclobutyl carbinyl cation rear-... 

The central bond of the l-(arylsulfonyl)bicyclo[1.1.0]butane system behaves like the double bond of a, /i-unsaturated sulfones to give alkyl-substituted cyclobutyl aryl sulfones on treatment with organometallic reagents (equation 20)17. This method has been applied... 

The system is evacuated to a pressure of 5-10 mm., and the tube is heated to 700°, measured at the center of the heated zone. 2-Chloro-2,3,3-trifluorocycIobutyl acetate is admitted at the rate of 10-20 g. per hour. From 70 g. (0.35 mole) of the cyclobutyl acetate there is obtained 62-68 g. of mixed solid and liquid condensate (Note 10). Fractionation through a 30-cm. column packed with glass helices affords 30-35 g. (60-70%) of 1-chloro-1,4,4-trifluorobutadiene (Note 11), b.p. 50-51°, 1-3870 18-22... 

Bis-[biphenylyl-(4)]- 542 (4-Chlor-phenyl)-(4-methoxy-phenyl)- 410 Cyclobutyl- 151 Cyclohexyl- 151... 

The rearrangement of the intermediate alkyl cation by hydrogen or methyl shift and the cyclization to a cyclopropane by a CH-insertion has been studied by deuterium labelling [298]. The electrolysis of cyclopropylacetic acid, allylacetic acid or cyclo-butanecarboxylic acid leads to mixtures of cyclopropylcarbinyl-, cyclobutyl- and butenylacetamides [299]. The results are interpreted in terms of a rapid isomerization of the carbocation as long as it is adsorbed at the electrode, whilst isomerization is inhibited by desorption, which is followed by fast solvolysis. 

Cyclobutyl substrates also solvolyze abnormally rapidly and give similar products. Furthermore, when the reactions are carried out with labeled substrates, considerable, though not complete, scrambling is observed. For these reasons, it has been suggested that a common intermediate (some kind of nonclassical intermediate, e.g., 25, p. 408) is present in these cases. This common intermediate could then be obtained by three routes ... 

This rearrangement, which accounts for the scrambling, is completely stereospecific.The rearrangements probably take place through a nonplanar cyclobutyl cation intermediate or transition state. The formation of cyclobutyl and homoallylic products from a cyclopropyl-methyl cation is also completely stereospecific. These products may arise by direct attack of the nucleophile on 58 or on the cyclobutyl cation intermediate. A planar cyclobutyl cation is ruled out in both cases because it would be symmetrical and the stereospecificity would be lost. 

The rate enhancement in the solvolysis of secondary cyclobutyl substrates is probably caused by participation by a bond leading directly to 58, which accounts for the fact that solvolysis of cyclobutyl and... 

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