A bishomo square-pyramidal carbonium ion

Kemp-Jones, A. V.; Nakamura, Nobuo; Masamune, Satoru

doi:10.1039/c39740000109

Cited by 30 publications

(24 citation statements)

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“…13C spectra are generally quite sensitive to a change of geometry and charge density and these factors apparently bring about an upfield shift for carbon 8 and a downfield shift for C-2 and -4, compared with those of the corresponding carbons in 1, although the magnitude of the chemical shift change is not large. Thus, at present we may conclude that the cation derived either from 3 or 4 can safely be represented by 2, but the above departure in the 13C chemical shift is in line with the trend we have observed for the square pyramidal carbocation (4,5,6) and the structure 2c might make some contribution. In either case, the charge is delocalized so extensively that it is not even clear at which carbon atom most of the charge resides.…”

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confidence: 66%

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The Trishomocyclopropenyl Cation. II. An Ethano-bridged Derivative

Masamune¹,

Sakai²,

Kemp-Jones³

1974

Can. J. Chem.

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An ethano-bridged trishomocyclopropeny1 carbonium ion has been generated in superacid media from 8-chlorotricyclo[3.2.1.02~4]octane and/or 4-chlorotricyclo[3.3.0.02~8]octane. The ' H and I3C n.m.r. spectra of this new stable carbonium ion compare well with those of the parent trishomocyclopropenyI carbonium ion and yet show some indication that the degree of charge delocalization is more extensive than that originally implied.On a produit un ion carbonium tthano-pontt du trishomocyclopropenyle dans un milieu superacide a partir du chloro-8 tricycl0[3.2.1.0~~~]octane et/ou du chloro-4 tricycl0[3.3.0.0~~~]-octane. Les spectres r.m.n. du ' H et du I3C de ce nouveau carbocation stable se comparent bien avec ceux de I'ion carbonium parent du trishomocyclopropenyle. Cependant ces spectres montrent que le degrt de delocalisation de charge est plus tlevt qu'il n'ttait prtiru a I'origine.[ The successful preparation of the parent trishomocyclopropenyl cation (1) of C , , symmetry (1) has encouraged us to generate the carbocation (2) in superacid media from now available 8-chlorotricyclo[3.2.1 .02.4]octane (3) (2) and/or 4-chlorotricyclo[3.3.0.02~8]octane (4) (3).2 We expected that this structural modification (by means of an ethano-bridge) introduced into 1 would only slightly perturb the electronic structure of 1 but yet, in view of our recent work on the related systems (4-6), would provide further information on the degree of electron delocalization in the entire system of 4. Results are summarized below (Scheme 1).As noted previously (1, 4, 6), chlorides appear to serve as the best precursors for the generation of cations in the present case. Thus, extraction of the chlorides 3 or 4 in CD2CI, with SbFSS02ClF at -120" provided yellow solutions which exhibited identical, clearly resolved 13Cand 'H n.m.r. spectra as shown in Figs. 1 and 2.All the signals remained virtually unchanged up to -40" and quenching the solutions with Na2C03 in methanol at -80" yielded a methoxy compound, almost certainly 5, identical with material obtained by solvolysis of 6 in a K2C03-methanol mixture (3). These experiments demonstrate that there was formed a stable, spectrally well-characterized carbocation.In order to define the structure of the new 'The author is grateful to the National Research Council and Hoffmann-LaRoche, Inc. for financial support.ZCompound 4 was prepared by treating 10 with SOCI,.cation, the unambiguous assignment of the n.m.r. signals to the nuclei is of prime importance and calls for the preparation of two deuterated precursors, 7 and 8. While the synthesis of 7 was readily accomplished through reduction of ketone 9 with deuterium over platinum (CH,OD) (3a) and then treatment of the resulting monodeuterated hydroxy compound (10-dl) with SOC1,,2 the four deuterium atoms in 8 were incorporated at an early stage of the reaction sequence (3a), i.e., reduction of chloroketal 11 using sodium in a (CH,),COD--tetrahydrofuran mixture.The 'H and 13C spectra of the new cation both show the presence of two-fold symmetry in this...

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supporting

confidence: 66%

“…As noted previously (1,4,6), chlorides appear to serve as the best precursors for the generation of cations in the present case. Thus, extraction of the chlorides 3 or 4 in CD2CI, with SbFSS02ClF at -120" provided yellow solutions which exhibited identical, clearly resolved 13C…”

mentioning

confidence: 63%

The Trishomocyclopropenyl Cation. II. An Ethano-bridged Derivative

Masamune¹,

Sakai²,

Kemp-Jones³

1974

Can. J. Chem.

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“…We thus conclude that the most likely assignment for the new bands detected is isomer 9, the 1,3-dimethyl cyclopentadienyl cation, which we indicate as DMCPD + . It is conceivable that we have missed an isomer in the list of those identified, but the isomers considered represent essentially all of those studied previously for C 7 H 9 + [25,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45]. It is also conceivable that minor amounts of other isomers in our list are also present, considering the signal level in the experiment.…”

Section: Resultsmentioning

confidence: 85%

“…CH 3 C 6 H 7 + ); the para structure is the most stable of these [25,29,31,36,40,41]. Several higher energy isomers have been studied experimentally [32,33,[37][38][39] and with theory [34,41,42,44,45]. Recently, we attempted to measure the infrared spectrum of the infamous 2-norbornyl cation (C 7 H 11 + ) in the gas phase, using protonation of a norbornene precursor [46].…”

Section: Introductionmentioning

confidence: 97%

“…Here we use different precursors and find a previously unanticipated isomer of this system. C 7 H 9 + ions have been investigated previously using mass spectrometry [27][28][29][30][31][32][33][34][35], NMR spectroscopy [36][37][38][39] infrared spectroscopy [25,40,41], and computational chemistry [25,27,40,41,44]. Four isomers of protonated toluene are known, corresponding to methyl substitution at different ring positions around the benzenium ring (i.e.…”

Section: Introductionmentioning

confidence: 99%

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