First formation of 1,1-dihalo-1,3-butadienes from reactions of dichloro- and dibromocarbenes with cyclopropenes via new addition-rearrangements

Weber, J.; Xu, Linfeng; Brinker, Udo H.

doi:10.1016/s0040-4039(00)61306-0

Cited by 30 publications

(41 citation statements)

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“…Two-step mechanisms for carbene addition to olefins were discussed previously by Jones and Moss. [4] While the recent computational investigation of Merrer and Rablen [48] does not lend support to the existence of intermediates in the reaction of CCl 2 with cyclopropenes, [49][50][51][52] the rearrangements of vinyl-substituted cyclopropylcarbenes are best rationalized by a diradicaloid intermediate. [53,54] The computational analysis of the ethylene + CF 2 reaction by Bernardi et al [55] at the (4,4)-CASSCF/6-31G* level suggested a two-step mechanism with a diradical intermediate having a barrier to ring closure of only 0.2 kcal mol À1 .…”

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confidence: 99%

Addition of Carbenes to the Sidewalls of Single‐Walled Carbon Nanotubes

Bettinger

2006

Chemistry A European J

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The addition of carbenes CX(2) (X=H, Cl) to single-walled carbon nanotubes (SWNTs) was investigated by density functional theory and finite, hydrogen-terminated nanotube clusters or periodic boundary conditions in conjunction with basis sets of up to polarized triple-zeta quality. For armchair [(3,3) to (12,12)] and zigzag tubes [(3,0) to (18,0)], reaction of CH(2) with the C--C bond oriented along the tube axis (A) is less exothermic than with those C--C bonds having circumferential (C) orientation. This preference decreases monotonically with increasing tube diameter for armchair, but not for zigzag tubes; here, tubes with small band gaps have a very low preference for circumferential addition. Axial addition results in cyclopropane products, while circumferential addition produces "open" structures for both armchair and zigzag tubes. The barriers for addition of dichlorocarbene to a (5,5) SWNT, studied for a finite C(90)H(20) cluster, are higher than that for addition to C(60), in spite of similar diameters of the carbon materials. Whereas addition of CCl(2) to [60]fullerene proceeds in a concerted fashion, addition to a (5,5) armchair SWNT is predicted to occur stepwise and involve a diradicaloid intermediate according to B3LYP, PBE, and GVB-PP computations. Addition to C bonds of (5,5) armchair tubes resulting in the thermodynamically more stable insertion products is kinetically less favorable than that to A bonds yielding cyclopropane derivatives.

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confidence: 99%

Addition of Carbenes to the Sidewalls of Single‐Walled Carbon Nanotubes

Bettinger

2006

Chemistry A European J

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“…55 In a similar manner, the reaction with cyclobutene does not provide dibromohousane but gives 2,3-dibromocyclopentene (Scheme 17). 56 With the more strained 1,2-diphenylcyclopropene the expected cyclobutene is accompanied by 1,1- dibromo-2,3-diphenylbuta-1,3-diene. These products arise, respectively, by conventional cyclopropyl-to-allyl ring cleavage and recapture of the bromide anion (Scheme 17, path a) and by nucleophilic addition of the tribromomethyl anion to the cyclopropene followed by ring opening and ejection of bromide ion (Scheme 17, path b).…”

Section: Scheme 15mentioning

confidence: 99%

Electrocyclic Ring-Opening Reactions of gem-Dibromocyclopropanes in the Synthesis of Natural Products and Related Compounds

Halton¹,

Harvey²

2006

Synlett

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“…In paths B and C, R′CCl adds to 3a in a stepwise manner via a diradical (path B) or zwitterion (path C) followed by concurrent ring contraction and rearrangement to 4a. These proposed stepwise paths are rooted in evidence provided by Brinker's group of a polar transition state, if not a full zwitterionic intermediate, and the stepwise character of dihalocarbene additions to 1,2-diarylcyclopropenes, 22,23 as well as the involvement of a zwitterionand thus a nonconcerted pathwayin singlet carbene addition to bicyclo[1.1.0]butanes proposed by Rablen et al 27 Path D depicts the possibility of the concerted addition and ring contraction of R′CCl + 3a → 4a. Path D has a lot of concurrent motion and may seem unconventional, but it is not unfounded, as it parallels the route by which CCl 2 adds to cyclopropene to produce a 1,1-dichloro-1,3-butadiene (Scheme 4).…”

Section: ■ Introductionmentioning

confidence: 96%

Experimental and Computational Mechanistic Investigation of Chlorocarbene Additions to Bridgehead Carbene–Anti-Bredt Systems: Noradamantylcarbene–Adamantene and Adamantylcarbene–Homoadamantene

et al. 2015

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Cophotolysis of noradamantyldiazirine with the phenanthride precursor of dichlorocarbene or phenylchlorodiazirine in pentane at room temperature produces noradamantylethylenes in 11% yield with slight diastereoselectivity. Cophotolysis of adamantyldiazirine with phenylchlorodiazirine in pentane at room temperature generates adamantylethylenes in 6% yield with no diastereoselectivity. (1)H NMR showed the reaction of noradamantyldiazirine + phenylchlorodiazirine to be independent of solvent, and the rate of noradamantyldiazirine consumption correlated with the rate of ethylene formation. Laser flash photolysis showed that reaction of phenylchlorocarbene + adamantene was independent of adamantene concentration. The reaction of phenylchlorocarbene + homoadamantene produces the ethylene products with k = 9.6 × 10(5) M(-1) s(-1). Calculations at the UB3LYP/6-31+G(d,p) and UM062X/6-31+G(d,p)//UB3LYP/6-31+G(d,p) levels show the formation of exocyclic ethylenes to proceed (a) on the singlet surface via stepwise addition of phenylchlorocarbene (PhCCl) to bridgehead alkenes adamantene and homoadamantene, respectively, producing an intermediate singlet diradical in each case, or (b) via addition of PhCCl to the diazo analogues of noradamantyl- and adamantyldiazirine. Preliminary direct dynamics calculations on adamantene + PhCCl show a high degree of recrossing (68%), indicative of a flat transition state surface. Overall, 9% of the total trajectories formed noradamantylethylene product, each proceeding via the computed singlet diradical.

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First formation of 1,1-dihalo-1,3-butadienes from reactions of dichloro- and dibromocarbenes with cyclopropenes via new addition-rearrangements

Cited by 30 publications

References 13 publications

Addition of Carbenes to the Sidewalls of Single‐Walled Carbon Nanotubes

Addition of Carbenes to the Sidewalls of Single‐Walled Carbon Nanotubes

Electrocyclic Ring-Opening Reactions of gem-Dibromocyclopropanes in the Synthesis of Natural Products and Related Compounds

Experimental and Computational Mechanistic Investigation of Chlorocarbene Additions to Bridgehead Carbene–Anti-Bredt Systems: Noradamantylcarbene–Adamantene and Adamantylcarbene–Homoadamantene

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