THE REACTION OF PHENYLBENZOYLDIAZOMETHANE WITH BENZOIN<sup>1</sup>

Curtin, David Y.; Proops, William R.

doi:10.1021/jo01370a021

Cited by 18 publications

(23 citation statements)

References 2 publications

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“…It is easiest to conceive of the process by assuming that the two irradiations are conducted at different wavelengths and in series, but the principle applies equally if the wavelengths are the same and the processes therefore occur in parallel. Although not necessarily intuitive, this is merely an application of the CurtinHammett principle (42).…”

Section: Resultsmentioning

confidence: 99%

Combinatorial discovery of two-photon photoremovable protecting groups

Pirrung

Pieper²,

Kaliappan³

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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A design principle for a two-photon photochemically removable protecting group based on sequential one-photon processes has been established. The expected performance of such groups in spatially directed photoactivation͞photodeprotection has been shown by a kinetic analysis. One particular molecular class fitting into this design, the nitrobenzyl ethers of o-hydroxycinnamates, has been presented. An initial demonstration of two-photon deprotection of one such group prompted further optimization with respect to photochemical deprotection rate. This was accomplished by the preparation and screening of a 135-member indexed combinatorial library. Optimum performance for >350 nm deprotection in organic solvent was found with 4,5-dialkoxy and ␣-cyano substitution in the nitrobenzyl group and 4-methoxy substitution in the cinnamate.

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Section: Resultsmentioning

confidence: 99%

Combinatorial discovery of two-photon photoremovable protecting groups

Pirrung

Pieper²,

Kaliappan³

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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“…The constraint of keeping K eq1 fixed makes this analysis impossible, but lifting this constraint makes it impossible to define an unequivocal control factor. The reason is that the control factor can only analyze the response to a transition-state change, and in this case we are changing an intermediate (this issue was tackled in different ways by the "degree of turn-over frequency (TOF) control", [3,40] the "thermodynamic rate control for intermediates", [41,42] the "thermodynamic control factor", [43] the "sensitivity", [18,44] and qualitatively by the Curtin-Hammett [45] and Sabatier classical principles [46] ). Let us recapitulate the deficiencies of IUPAC definition of a RD-Step:…”

Section: Thementioning

confidence: 99%

“…[3,4,7] The net chemical flow in an exothermic reaction in the steady state is always in the forward direction; this fact will be the first clue to find the RD-States in a catalytic cycle. The second clue is that from each intermediate we can consider the effective energy barrier to be crossed as the highest energy transition state that occurs in the forward direction (this can be thought as the Curtin-Hammett principle applied to catalytic cycles [45] ). The RD-States are the ones that have the highest effective energy barrier.…”

Section: Rd-states In Catalysis 41 Introduction To Catalytic Cyclesmentioning

confidence: 99%

The Rate‐Determining Step is Dead. Long Live the Rate‐Determining State!

2011

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The concept of a rate-determining step (RD-Step) is central to the kinetics community, and it is basic knowledge even for the undergraduate chemical student. In spite of this, too many different definitions of the RD-Step appear in the literature, all of them with drawbacks. This dilemma has been thoroughly studied by several authors in the attempt to "patch" the drawbacks and bring the RD-Step to a correct physical meaning. Herein we review with simple models the most notable definitions and some challengers of the RD-Step concept, to conclude with the deduction that there are no rate-determining steps, only rate-determining states.

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“…Due to the Curtin-Hammett principle [58][59][60], their relative stability is not important since the TS along the branched or linear reaction paths are significantly higher, as shown in the next Section, than the barriers between them (*5.5 kcal/mol for 2S,3R; *2 or *7 kcal/mol for 2S,3S). The locations of the other species (f) are also shown in Fig.…”

Section: Reactant Complexesmentioning

confidence: 99%

The fate of branched and linear isomers in the rhodium-catalyzed hydroformylation of 3,4,4-trimethylpent-1-ene

Alagona

Ghio

2012

Theor Chem Acc

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In nonreversible hydroformylations, the computational evaluation of regio-and stereoselectivities from the relative energy barriers of the transition states (TS) for the alkyl-Rh intermediate formation step is possible, provided all low energy conformers are considered. In contrast, in reversible hydroformylations, also the subsequent reaction steps need to be taken into account to shed some light on mechanistic details. Thus, an extensive comparison of branched (B) and linear (L) reaction pathways for the Rh-catalyzed hydroformylation of 3,4,4-trimethylpent-1-ene (a bulky chiral substrate), going from a number of reactant complexes to products, has been carried out to rationalize the experimental result that pointed to reaction reversibility, although the value of the regioselectivity ratio (B:L = 15:85), based on alkyl-Rh TS free energies, computed under the hypothesis of nonreversibility, was in satisfactory agreement with the experimental one (5:95). A density functional theory approach at the B3P86/6-31G* level coupled to effective core potentials for Rh in the LanL2DZ valence basis set has been employed. By comparing the activation free energies involved in the various steps for the different reactant adducts, interestingly a similar behavior along all the linear pathways is found: the alkyl-Rh formation TS presents the highest barrier; thus, the reaction is nonreversible for all the linear isomers that invariably proceed to yield the linear aldehyde. Conversely, the behavior is quite different along the branched pathways. While some branched isomers eventually produce the corresponding aldehydes, two of the others follow distinct competing pathways, because b-hydride elimination occurs (a) to the terminal olefin-Rh complex (the starting material) that reacts again with the original regioselectivity, increasing the linear fraction, when the CO addition and insertion TS are higher than the alkyl-Rh TS and (b) to the internal olefin-Rh complex when the CO addition and insertion TS are higher than the relevant b-hydride elimination TS, but not than the alkyl-Rh TS. The solvent effect on the reversible profile, evaluated either in the supermolecule approach by adding a benzene molecule to the calculations or in the IEF-PCM framework (e = 2.247), does not bring about any substantial change in the profile, leaving unaltered the conclusions reached.

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THE REACTION OF PHENYLBENZOYLDIAZOMETHANE WITH BENZOIN¹

Cited by 18 publications

References 2 publications

Combinatorial discovery of two-photon photoremovable protecting groups

Combinatorial discovery of two-photon photoremovable protecting groups

The Rate‐Determining Step is Dead. Long Live the Rate‐Determining State!

The fate of branched and linear isomers in the rhodium-catalyzed hydroformylation of 3,4,4-trimethylpent-1-ene

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THE REACTION OF PHENYLBENZOYLDIAZOMETHANE WITH BENZOIN1

Cited by 18 publications

References 2 publications

Combinatorial discovery of two-photon photoremovable protecting groups

Combinatorial discovery of two-photon photoremovable protecting groups

The Rate‐Determining Step is Dead. Long Live the Rate‐Determining State!

The fate of branched and linear isomers in the rhodium-catalyzed hydroformylation of 3,4,4-trimethylpent-1-ene

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Product

Resources

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THE REACTION OF PHENYLBENZOYLDIAZOMETHANE WITH BENZOIN¹