Cyclobutyl chloride

When a gaseous flow of cyclopropylcarbinyl chloride is passed over NaY zeolite at room temperature, formation of cyclobutyl chloride and allylcarbinyl chloride was observed (scheme 4), as well as cyclopropylcarbinyl chloride (product and unreacted starting material). These data are consistent with formation of the C4H7+ cation with internal return of the chloride ion. 

The 3-ewrfo-(trimethylsilyl)bicyclobutonium ion 431 is also obtained directly from a four-membered-ring progenitor, i.e. 3-(trhnethylsilyl)cyclobutyl chloride 432, by reaction... 

The cyclopropylmethyl cation has recently been generated in the gas phase from both homoallyl chloride and cyclopropylmethyl chloride and studied using collisional activated dissociation mass spectrometry.216 Interestingly, cyclobutyl chloride, which yields the cyclopropylmethyl cation in the condensed phase, gives a substantial amount of the bicyclobutonium ion in the gas phase. 

C H7 ions were generated by collisionally activated dissociation (CAD) in the gas phase from various precursors.216Mass spectrometric analysis showed thathomoallyl chloride and cyclopropylmethyl chloride generated primarily cation 521, whereas cyclobutyl chloride gave a substantial amount of bicyclobutonium ion 522. 

A modified Hunsdiecker synthesis is reported by Dupont and coworkers, who have prepared cyclobutyl chloride by chlorodecarboxylation in presence of lead tetracetate (equation 169)1090. 

Cyclobutyl chloride does not react with Ph2P- ions in the dark or under photostimulation in liquid ammonia. On the contrary, cyclobutyl bromide (77) reacts with Ph2P ions in the dark (15 min, 42% of substitution product 78) as well as under photostimulation (83% of substitution) (equation 64). p-DNB does not affect the dark reaction while it partially inhibits the light catalysed one. In the latter case, the amount of product obtained is similar to that formed under dark condition151. 

Cyclobutanone-3-carboxylic acid, 357 Cyclobutanones, 357 Cyclobutylamine, 376 Cyclobutyl chloride, 463 Cyclobutyl phenyl ketoxime, 289 cis,cis-, 6-Cyclodecadiene, 275 Cyclodecane, 246... 

Roberts and Mazur1 reported that treatment of a mixture of cyclopropylcarbinyl chloride and cyclobutyl chloride (approximately 2 1) with zinc chloride in coned, hydrochloric acid (Lucas reagent2) gave allylcarbinyl chloride in 46% yield. They also isomerized the corresponding bromides with zinc bromide in 48% hydrobromic acid. 

Another valuable alternative to the Hunsdiecker reaction is the Kochi modification,3 which employs a Pb(IV) reagent. It is a one-carbon oxidative degradation of carboxylic acids and is suitable for synthesis of secondary and tertiary chlorides as exemplified by the transformation of carboxylic acid 10 to cyclobutyl chloride (11) mediated by lead tetra-acetate (LTA).16 Further improvement of the Kochi modification employs LTA under milder conditions where N-chlorosuccinimide (NCS) is used as chlorinating agent and a mixture of DMF and HOAc as solvent.17... 

All these fairly similar results are, however, in sharp contrast to solvolysis of cyclopropylmethyl chloride, which is much more reactive than cyclobutyl chloride or 4-chlorobut-2-ene (Roberts and Mazur, 1951 a). There was also positive evidence for internal return in the cyclopropylmethyl chloride solvolysis, although the solvent used (50 aqueous ethanol) is known to be unfavorable for internal return. Another reaction, closely related to the protolysis of cyclopropyldiazomethane mentioned above, is the reaction of that diazoalkane with ethereal benzoic acid. The product ratio cyclopropylmethanol cyclobutanol = 5.8 indicated a strong decrease of skeletal rearrangement (Moss and Shulman, 1968). 

Silyl-substituted bicyclobutonium ions are also accessible from direct ionization of 3-silyl-sub-stituted cyclobutyl chlorides. Matrix co-condensation of cw//ra s-3-(trimethylsilyl)cyclobutyl chloride (Scheme 1, D (R = R = Me)) with SbFs onto a surface of SO2CIF/SO2F2 at -196°C yields after homogenization at -130°C a yellow solution of carbocation 12. The C-NMR spectrum obtained for cation 12, except for the alkyl groups at silicon, is very similar to the C-NMR spectrum of carbocation 9. The differences of the signals for the Co-, Cp/Cp -carbons are smaller than 1 ppm. 

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