Mechanisms of ring contraction, C—H insertion and 1,2‐hydrogen migration of cyclobutylidene

Wang, Bingze; Deng, Chao

doi:10.1002/cjoc.19900080203

Cited by 3 publications

(3 citation statements)

References 13 publications

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“…Later, Sulzbach et al (1997) studied the structure and rearrangements of cyclobutylidene using hybrid Hartree-Fock/density functional theory, Møller-Plesset perturbation theory, and coupled cluster methods. 23 The BHandHLYP/DZP and CCSD(T)/DZP computations both showed preference for 1,2-H migration, which is consistent with Wang and Deng's results 42 but not with experiment. 17,36,37 After including electron correlation and increasing the basis set size, the transition state for 1,2-C migration was found to be much more affected than that for 1,2-H migration.…”

Section: Introductionsupporting

confidence: 74%

“…, which is consistent with Wang and Deng's results. 42 Moreover, while HF theory tends to overestimate all of the barriers, MP2 over-compensates the correlation energy for 1,2-C migration. This explains the erratically ''correct'' prediction by MP2 in Sulzbach and co-worker's study.…”

Section: Relative Energies and Reaction Ratesmentioning

confidence: 99%

“…Wang and Deng (1990) conducted a comprehensive theoretical investigation on the singlet potential energy surface at the HF/6-31G**//HF/6-31G level of theory. 42 The barriers to rearrangement from cyclobutylidene to methylenecyclopropane, cyclobutene, and bicyclobutane were reported to be 18.6, 17.9 and 26.3 kcal mol À1 , respectively, slightly flavoring 1,2-H migration. Later, Sulzbach et al (1997) studied the structure and rearrangements of cyclobutylidene using hybrid Hartree-Fock/density functional theory, Møller-Plesset perturbation theory, and coupled cluster methods.…”

Section: Introductionmentioning

confidence: 99%

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Characterizing a nonclassical carbene with coupled cluster methods: cyclobutylidene

Wang

Agarwal

Schaefer

2016

Phys. Chem. Chem. Phys.

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Carbenes represent a special class of reactive compounds that possess a lone pair of electrons on a carbon atom. Among the myriad examples of carbenes in the literature, cyclobutylidene stands out as a unique nonclassical compound that includes transannular interaction between opposing C1 and C3 carbon atoms within a four-membered ring. On its lowest potential energy surface (X[combining tilde](1)A'), cyclobutylidene quickly rearranges, following three reaction paths: (i) 1,2-H migration; (ii) 1,2-C migration; and, (iii) 1,3-H migration. Herein, this reactivity is examined with high-level coupled-cluster methods [up to CCSDT(Q)]. At this level of theory, combined with extrapolation techniques to obtain energies at the complete basis set (CBS) limit, the long-standing disparity between theoretical and experimental results is resolved. Specifically, cyclobutylidene is predicted to prefer 1,2-C migration rather than 1,2-H migration. Rate constants for the three reaction paths are obtained from canonical variational transition state theory (CVT) and yield reasonable agreement with existing experimental results. Further characterization of cyclobutylidene is also reported: the singlet-triplet gap (ΔES-T) is found to be -9.3 kcal mol(-1) at the CCSDT(Q)/CBS level of theory, and anharmonic vibrational frequencies are determined with second-order vibrational perturbation theory (VPT2).

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Section: Introductionsupporting

confidence: 74%

Section: Relative Energies and Reaction Ratesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterizing a nonclassical carbene with coupled cluster methods: cyclobutylidene

Wang

Agarwal

Schaefer

2016

Phys. Chem. Chem. Phys.

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Synthesis of Methylene‐ and Alkylidenecyclopropane Derivatives

Audran

Pellissier

2010

Adv Synth Catal

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Since the methylenecyclopropane moiety is found in many biologically active natural substances, the synthesis of methylene-and alkylidenecyclopropanes remains a considerable challenge. In addition, an attractive feature is their surprising stability, accompanied by a high level of strain, conferring on them an otherwise unattainable chemical reactivity. The growing interest in the chemistry of these compounds has in its turn stimulated the development of alternative approaches to their skeleton, aimed at selectively introducing structural and chemical diversification. The three principal methods to synthesize these important compounds are based on the formation of the cyclopropane ring, the use of preformed cyclopropanes, and the use of preformed methyleneand alkylidenecyclopropanes.

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Regioselective Formation of Alkylidenecyclopropanes from 2-Substituted Cyclobutylidenes Generated from Geminal Dibromocyclobutanes and Methyllithium

2004

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Four different 2-substituted geminal dibromocyclobutanes were reacted with methyllithium at -78 degrees C. In contrast to previous studies using diazocyclobutanes as carbene precursors at temperatures above 200 degrees C via reaction of the corresponding tosylhydrazone sodium salts, the organometallic route in each case produces only an alkylidenecyclopropane that could be isolated in good yields. B3LYP calculations were employed to rationalize the observed regioselective ring contraction of the generated cyclobutyliden(oid)s. [reaction: see text]

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Mechanisms of ring contraction, C—H insertion and 1,2‐hydrogen migration of cyclobutylidene

Cited by 3 publications

References 13 publications

Characterizing a nonclassical carbene with coupled cluster methods: cyclobutylidene

Characterizing a nonclassical carbene with coupled cluster methods: cyclobutylidene

Synthesis of Methylene‐ and Alkylidenecyclopropane Derivatives

Regioselective Formation of Alkylidenecyclopropanes from 2-Substituted Cyclobutylidenes Generated from Geminal Dibromocyclobutanes and Methyllithium

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