29342-65-2Relevant academic research and scientific papers
Correlation of gas-phase stability of bridgehead carbocations with rates of solvolysis and ab initio calculations
Abboud, José-Luis M.,Casta?o, Obis,Della, Ernest W.,Herreros, Marta,Müller, Paul,Notario, Rafael,Rossier, Jean-Claude
, p. 2262 - 2266 (1997)
The stability of bridgehead carbocations has been determined by Fourier transform ion cyclotron resonance spectroscopy (FT ICR) based on dissociative proton attachment (DPA) of bromides and alcohols. The stability of the ions correlates with the solvolytic reactivity of bridgehead derivatives over a rate range of 23 log units, and with theoretical calculations for hydride transfer of bridgehead hydrocarbons at the MP2/6-311G** level.
Aqueous Microdroplets Capture Elusive Carbocations
Kumar, Anubhav,Mondal, Supratim,Banerjee, Shibdas
supporting information, p. 2459 - 2463 (2021/02/16)
Carbocations are short-lived reactive intermediates in many organic and biological reactions that are difficult to observe. This field sprung to life with the discovery by Olah that a superacidic solution allowed the successful capture and nuclear magnetic resonance characterization of transient carbocations. We report here that water microdroplets can directly capture the fleeting carbocation from a reaction aliquot followed by its desorption to the gas phase for mass spectrometric detection. This was accomplished by employing desorption electrospray ionization mass spectrometry to detect a variety of short-lived carbocations (average lifetime ranges from nanoseconds to picoseconds) obtained from different reactions (e.g., elimination, substitution, and oxidation). Solvent-dependent studies revealed that aqueous microdroplets outperform organic microdroplets in the capture of carbocations. We provide a mechanistic insight demonstrating the survival of the reactive carbocation in a positively charged aqueous microdroplet and its subsequent ejection to the gas phase for mass spectrometric analysis.
Decarboxylative Bromination of Sterically Hindered Carboxylic Acids with Hypervalent Iodine(III) Reagents
Kanazawa, Junichiro,Koyamada, Kenta,Miyamoto, Kazunori,Uchiyama, Masanobu,Watanabe, Ayumi
supporting information, p. 1328 - 1334 (2020/08/14)
Sterically hindered three-dimensional (3D) alkyl halides are promising precursors for various reactions; however, they are difficult to synthesize via conventional reactions. We present an efficient and practical method for decarboxylative bromination of sterically hindered 3D aliphatic carboxylic acids using commercially available (diacetoxyiodo)benzene and potassium bromide, one of the most stable and cheapest bromine sources in nature. The present method features a metal-free/Br2-free system, mild reaction conditions, one-pot operation under air at room temperature, wide functional group compatibility, and gram-scale synthetic capability. This highly efficient reaction cleanly converts a broad range of carboxylic acids, the most inexpensive and readily available sources of highly strained/naturally occurring/drug-related scaffolds, into the corresponding alkyl bromides in good to high yields.
Selective C-H halogenation over hydroxylation by non-heme iron(iv)-oxo
Rana, Sujoy,Biswas, Jyoti Prasad,Sen, Asmita,Clémancey, Martin,Blondin, Geneviève,Latour, Jean-Marc,Rajaraman, Gopalan,Maiti, Debabrata
, p. 7843 - 7858 (2018/10/31)
Non-heme iron based halogenase enzymes promote selective halogenation of the sp3-C-H bond through iron(iv)-oxo-halide active species. During halogenation, competitive hydroxylation can be prevented completely in enzymatic systems. However, synthetic iron(iv)-oxo-halide intermediates often result in a mixture of halogenation and hydroxylation products. In this report, we have developed a new synthetic strategy by employing non-heme iron based complexes for selective sp3-C-H halogenation by overriding hydroxylation. A room temperature stable, iron(iv)-oxo complex, [Fe(2PyN2Q)(O)]2+ was directed for hydrogen atom abstraction (HAA) from aliphatic substrates and the iron(ii)-halide [FeII(2PyN2Q)(X)]+ (X, halogen) was exploited in conjunction to deliver the halogen atom to the ensuing carbon centered radical. Despite iron(iv)-oxo being an effective promoter of hydroxylation of aliphatic substrates, the perfect interplay of HAA and halogen atom transfer in this work leads to the halogenation product selectively by diverting the hydroxylation pathway. Experimental studies outline the mechanistic details of the iron(iv)-oxo mediated halogenation reactions. A kinetic isotope study between PhCH3 and C6D5CD3 showed a value of 13.5 that supports the initial HAA step as the RDS during halogenation. Successful implementation of this new strategy led to the establishment of a functional mimic of non-heme halogenase enzymes with an excellent selectivity for halogenation over hydroxylation. Detailed theoretical studies based on density functional methods reveal how the small difference in the ligand design leads to a large difference in the electronic structure of the [Fe(2PyN2Q)(O)]2+ species. Both experimental and computational studies suggest that the halide rebound process of the cage escaped radical with iron(iii)-halide is energetically favorable compared to iron(iii)-hydroxide and it brings in selective formation of halogenation products over hydroxylation.
PROCESS FOR THE PREPARATION OF ORGANIC BROMIDES
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Paragraph 00169; 00180; 00197, (2017/07/28)
The present invention provides a process for the preparation of organic bromides, by a radical bromodecarboxylation of carboxylic acids with a bromoisocyanurate.
Halogen-exchange reactions between alkyl fluorides and boron trihalides or tetrahalides. A convenient synthesis of alkyl halides from alkyl fluorides
Namavari, Mohammad,Satyamurthy, N.,Barrio, Jorge R.
, p. 89 - 93 (2007/10/02)
A simple and effective method for converting fluoroalkanes to their corresponding chloro-, bromo- and iodo-alkanes using commercially available boron trihalides and titanium tetrahalides is described. - Keywords: Halogen-exchange reactions; Alkyl fluorides; Boron trihalides; Titanium tetrahalides; NMR spectroscopy; Mass spectrometry
Hydroalumination of alkenes by the LiAlH4*3AlBr3 system
Gorobets, E. V.,Shitikova, O. V.,Lomakina, S. I.,Tolstikov, G. A.,Kuchin, A. V.
, p. 1573 - 1578 (2007/10/02)
The hydroalumination of a series of alkenes and some fused aromatic hydrocarbons by the LiAlH4*3AlBr3 system in low-polar solvents was studied.Alkenes with mono-, di-, tri-, and tetraalkyl substituted, mono- and diaryl substituted double bonds and anthracene react at room temperature to give the corresponding dibromoaluminoalkanes in high yields.Benzylidenefluorene, tetraphenylethylene, naphthalene, and phenanthrene do not undergo hydroalumination under these conditions.Camphene, bicyclooct-2-ene, and norbornene afford the corresponding organoaluminum compounds with high stereoselectivity.Oxidation and halo- and acyldemetallation of the resulting alkyl- and arylalanes were carried out.
The halogenolysis of organoboranes
Morrill,Lu,Brister,O'Shaughnessy,Belfield
, p. 973 - 976 (2007/10/02)
Transmercuration of tri-exo-2-norbornylborane followed by chlorinolysis of the resultant organoborane is a low yield (≤5%) method of producing exo-2-norbornyl chloride. The primary source of this low yield is the inefficient transmercuration of the sterically restricted organoborane. Yields of alkyl halide are substantially higher (up to 63%) when the organoborane undergoes direct chlorinolysis promoted by boron trichloride. Even higher yields (approaching 80%) are obtained when brominolysis of the organoborane is carried out. Controls suggest that at least part of the reason for the higher yield with bromine is due to the greater stability of the product under the reaction conditions. Despite the general retention aspects (exo-borane gives largely exo-halide) of these halogenolyses, deuterium labeling studies show that these reactions are accompanied by substantial Wagner-Meerwein rearrangement, very possibly due to boron trihalide induced rearrangement of the norbornyl halide product.
Photochemistry of alkyl halides. 12. Bromides vs Iodides
Kopp, Paul J.,Adkins, Rick L.
, p. 2709 - 2717 (2007/10/02)
Conditions have been developed for optimizing ionic photobehavior material balances from alkyl bromides. Hydroxide ion as an efficient for the byproduct HBr while giving minimal competing photoreduction via electron transfer to the alkyl bomide. The photobehavior of bromides 1, 11, 25, and 40 has examined and with that of the corresponding iodides 2, 12, 26, 41 under conditions. In each case, the bromide higher yields of products derived from out of cage radical intermidiates than the corresponding iodide. However, with the 2-norbornyl bromides 11 and iodides 12 showed that, of products not formed from the out of cage 2-norbornyl radical 13, the bromides 11 gave a higher percentage of products from the ionic intermediates 15 and 16 than did the iodides. Thus, electron transfer within the radical pair 14 is apparently more rapid for bromides than iodides, as expected on the of the relative electronegativities of bromine iodine. It is that the substantially higher yields of out of radical products from alkyl bromides may be due in to formation of the radical pair with greater excess energy, which results in more rapid escape from the cage. The epimeric 2-norbornyl bromides 11x and 11n underwent no detectable interconversion and afforded somewhat different product ratios. The more hindered epimer 11n underwent conversion to products at a slower than 11x. By contrast, 12x and 12n underwent substantial interconversion via out of transfer of an iodine atom from iodide 12 to radical 13. Epimerization was significantly attenuated in the more viscous solvent tert-butyl alcohol.
Base-Promoted 1,2-Eliminations from endo-2-Bicycloheptyl Halides and Arenesulfonates
Bartsch, Richard A.,Lee, Jong Gun
, p. 5247 - 5252 (2007/10/02)
Base-solvent systems that provide clean bimolecular 1,2-elimination from endo-2-bicycloheptyl halides and arenesulfonates by suppressing competitive solvolysis and nortricyclene-forming 1,3-elimination are developed.The stereochemistries of elimination from exo-3-deuterio-endo-2-bromobicycloheptane (10) and exo-3-deuterio-endo-2-bicycloheptyl 2,4,6-triisopropylbenzenesulfonate (11) are assessed using these base-solvent systems.The competitive syn-endo and anti-exo-H elimination modes are found to be strongly influenced by base association.However, for dissociated alkoxide bases, the elimination stereochemistry is unaffected by changes in leaving group from halide to arenesulfonate, in base strength, and in base size.
