Topic
Alkylation
About: Alkylation is a research topic. Over the lifetime, 29915 publications have been published within this topic receiving 464944 citations. The topic is also known as: alkylation reaction.
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TL;DR: It was suggested that the steric accessibility of the weakly nucleophilic phosphodiester group on the outside of the DNA macromolecule favours its reaction with ethylating, as opposed to methylating, reagents.
Abstract: 1. The ethyl phosphotriester of thymidylyl(3′-5′)thymidine, dTp(Et)dT, was identified as a product from reaction of DNA with N-ethyl-N-nitrosourea, by procedures parallel to those reported previously for the methyl homologue produced by N-methyl-N-nitrosourea. 2. Enzymic degradation to yield alkyl phosphotriesters from DNA alkylated by these carcinogens and by dimethyl sulphate and ethyl methanesulphonate was studied quantitatively, and the relative yields of the triesters dTp(Alk)dT were determined. The relative reactivity of the phosphodiester group dTpdT to each of the four carcinogens was thus obtained, and compared with that of DNA overall, or with that of the N-7 atom of guanine in DNA. Relative reactivity of the phosphodiester group was lowest towards dimethyl sulphate, the least electrophilic of the reagents used, and was highest towards N-ethyl-N-nitrosourea, the most electrophilic reagent. 3. The nature of the alkyl group transferred also influenced reactivity of the phosphodiester site, since this site was relatively more reactive towards ethylation than would be predicted simply from the known Swain-Scott s values of the alkylating agents. It was therefore suggested that the steric accessibility of the weakly nucleophilic phosphodiester group on the outside of the DNA macromolecule favours its reaction with ethylating, as opposed to methylating, reagents. 4. Taking a value of the Swain-Scott nucleophilicity (n) of 2.5 for an average DNA nucleotide unit [Walles & Ehrenberg (1969) Acta Chem. Scand. 23, 1080-1084], a value of n of about 1 for the phosphodiester group was deduced, and this value was found to be 2-3 units less than that for the N-7 atom of guanine in DNA. 5. The reactivity of DNA overall was markedly high towards the alkylnitrosoureas, despite their relatively low s values. This was ascribed to an electrostatic factor that favoured reaction of the negatively charged polymer with alkyldiazonium cation intermediates.
93 citations
TL;DR: In this paper, a diphenylamine-linked bis(imidazoline) ligand with trans-diphenyl substitution was proposed for the Friedel-Crafts alkylation of indole derivatives with nitroalkenes.
Abstract: The new diphenylamine-linked bis(imidazoline) ligands were prepared through Kelly-You’s imidazoline formation procedure mediated by Hendrickson’s reagent in good yields. The novel ligands were tested in the asymmetric Friedel–Crafts alkylation of indole derivatives with nitroalkenes. In most cases, good yields (up to 97%) and excellent enantioselectivities (up to 98%) can be achieved. The optimized bis(imidazoline) ligand with trans-diphenyl substitution on the imidazoline ring gave better enantioselectivity than the corresponding bis(oxazoline) ligand.
93 citations
TL;DR: In this article, a new one-step procedure for the synthesis of monoalkylated calix[4]arenes is presented, where the reaction of calix [4]-arene 1a or 1b with 1.2 equivalent of a weak base (K2CO3 in MeCN or CsF in DMF) and excess of alkylating agent affords the mono-alkylation calix in moderate to good yields
93 citations
TL;DR: Perfluoroalkylation of electron-rich aromatic compounds with trifluoromethyl bromide was performed in the presence of sodium dithionite or zinc-sulphur dioxide as mentioned in this paper.
Abstract: Perfluoroalkylation of electron-rich aromatic compounds with trifluoromethyl bromide, or long-chain perfluoroalkyl iodides, was performed in the presence of sodium dithionite or zinc–sulphur dioxide. This alkylation occurred at the ortho and para positions relative to the amino or hydroxy substituent. Pyrroles were perfluoroalkylated regioselectively at the 2-position. This alkylation was interpreted as a radical aromatic substitution; the formation of the perfluoroalkyl radical can be induced by a single-electron transfer from sulphur dioxide radical anion to the perfluoroalkyl halide.
93 citations
TL;DR: Functionalization significantly reduced the rate of surface oxidation in air compared to that of the H-terminated Si(100) surface, with alkylated surfaces forming less than half a monolayer of oxide after over one month of exposure to air.
Abstract: Single-crystal Si(100) surfaces have been functionalized by using a two-step radical chlorination−Grignard (R= MgCl, R = CH3, C2H5, C4H9, C6H5, or CH2C6H5) alkylation method. After alkylation, no chlorine was detectable on the surface by X-ray photoelectron spectroscopy (XPS), and the C 1s region showed a silicon-induced peak shift indicative of a Si−C bond. The relative intensity of this peak decreased, as expected, as the steric bulk of the alkyl increased. Despite the lack of full alkyl termination of the atop sites of the Si(100) surface, functionalization significantly reduced the rate of surface oxidation in air compared to that of the H-terminated Si(100) surface, with alkylated surfaces forming less than half a monolayer of oxide after over one month of exposure to air. Studies of the charge-carrier lifetime with rf photoconductivity decay methods indicated a surface recombination velocity of <30 cm s-1 for methylated surfaces, and <60 cm s-1 for Si surfaces functionalized with the other alkyl gro...
93 citations