Chemistry of bent bonds.  XLII.  Stereospecific rearrangement of strained cyclobutylcarbinyl cations

Gassman, Paul G.; Armour, Eugene A.

doi:10.1021/ja00799a057

Cited by 12 publications

(3 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…48 Other approaches toward the bicyclo[4.3.1]decene skeleton are depicted in Scheme 7. These include Wells' pyrolysis of a secondary benzoate (36 f 37), 55 a rearrangement discovered by Gassman in his solvolysis studies of bridgehead cyclopropane derivatives (38 f 39 and 40 f 39), 56,57 House's β-elimination of a tertiary bromide and an alkoxide (41 f 42 and 43 f 42), 58 and Bestmann's intramolecular Wittig olefination (44 f 42). 59 Some of these methods are quite high yielding and have paved the way for synthetic efforts directed at the phomoidrides (see below).…”

Section: Synthetic Studiesmentioning

confidence: 99%

The Art of Innovation in Organic Chemistry: Synthetic Efforts toward the Phomoidrides

et al. 2003

View full text Add to dashboard Cite

Section: Synthetic Studiesmentioning

confidence: 99%

The Art of Innovation in Organic Chemistry: Synthetic Efforts toward the Phomoidrides

et al. 2003

View full text Add to dashboard Cite

“…4,17 Although relatively less strained when compared to the cyclopropyl group, the cyclobutyl ring, in the puckered conformation, is stereoelectronically well positioned for the formation of nonclassical cyclobutylmethyl cations. 18,19 There is much precedence for the involvement of nonclassical cyclobutylmethyl cations as reaction intermediates based on early solvolytic studies on cyclobutylmethyl substrates. [19][20][21][22][23][24][25][26][27][28][29][30] We have recently prepared the first persistent cyclobutylmethyl cation, R,R-dicyclopropylcyclobutylmethyl cation, 4, in superacid media.…”

Section: Introductionmentioning

confidence: 99%

“…18,19 There is much precedence for the involvement of nonclassical cyclobutylmethyl cations as reaction intermediates based on early solvolytic studies on cyclobutylmethyl substrates. [19][20][21][22][23][24][25][26][27][28][29][30] We have recently prepared the first persistent cyclobutylmethyl cation, R,R-dicyclopropylcyclobutylmethyl cation, 4, in superacid media. 31 The latter carbocation shows distinct absorptions (δ 13 C) for the cyclopropyl C R and C R′ as well as C β and C β′ carbons indicating that it exists as a bisected conformer.…”

Section: Introductionmentioning

confidence: 99%

Structural Studies of Nonclassical Cyclobutylmethyl Cations by the ab initio Method

et al. 2007

View full text Add to dashboard Cite

Ab initio calculations at the MP2/cc-pVTZ level show that the cyclobutylmethyl cation is a nonclassical sigma-delocalized species, which is distinct from the global minimum C2-symmetric cyclopentyl cation (Schleyer, P. v. R.; Carneiro, J. W. de M.; Koch, W.; Raghavachari, K. J. Am. Chem. Soc. 1989, 111, 5475). Relatively lower level DFT calculations, on the other hand, show that the primary cyclobutylmethyl cation spontaneously collapses into the cyclopentyl cation (Prakash, G. K. S.; Reddy, V. P.; Rasul, G.; Casanova, J.; Olah, G. A. J. Am. Chem. Soc. 1998, 120, 13362). The secondary 1-cyclobutylethyl cation is also a nonclassical carbocation, as shown by calculations at the MP2/cc-pVTZ level. Two structures having energy minima are identified for the latter cation on the potential energy surface. The conformer in which the methyl group is in the exo orientation is a global minimum and is favored over the corresponding endo conformer by 1.2 kcal/mol at the MP2/cc-pVTZ//MP2/cc-pVTZ +ZPE level of calculations. The tertiary 1-cyclobutyl-1-methylethyl cation, at this level of calculations, also involves substantial nonclassical sigma-delocalization, showing that the nonclassical stabilization is more important for cyclobutylmethyl cations relative to the cyclopropylmethyl cations. The 13C NMR chemical shifts obtained from GIAO-CCSD(T)/tzp/dz calculations further substantiate the nonclassical structures for these carbocations.

show abstract

Die charakteristischen Eigenschaften homoaromatischer Systeme

Paquette

1978

Angew. Chem.

View full text Add to dashboard Cite

Verbindungen mit homoaromatischen Eigenschaften sind nach wie vor ein auflerordentlich interessantes Gebiet der Chemie. Derzeit wird u. a. versucht, das AusmaR der weitreichenden Delokalisierung von Elektronen experimentell zu bestimmen, die Wechselwirkungen in Molekiilen mit zwei oder mehr isolierenden Atomen zu ermitteln und energetische sowie geometrische Eigenschaften der homoaromatischen Systeme theoretisch abzuschatzen. In diesem Aufsatz werden in erster Linie neuere spektroskopische und strukturelle Befunde kritisch besprochen; daneben werden die Reaktionen analysiert, die den Zugang zu homoaromatischen Ionen ermoglichen. Ausfuhrlich diskutiert werden mono-, bis-und trishomoaromatische Systeme, und zwar getrennt nach kationischen, anionischen und neutralen Spezies. Zuvor wird kurz die Orbitaliiberlappung in diesen Verbindungen dargestellt.

show abstract

Chemistry of bent bonds. XLII. Stereospecific rearrangement of strained cyclobutylcarbinyl cations

Cited by 12 publications

References 1 publication

The Art of Innovation in Organic Chemistry: Synthetic Efforts toward the Phomoidrides

The Art of Innovation in Organic Chemistry: Synthetic Efforts toward the Phomoidrides

Structural Studies of Nonclassical Cyclobutylmethyl Cations by the ab initio Method

Die charakteristischen Eigenschaften homoaromatischer Systeme

Contact Info

Product

Resources

About