Alkylating agents comparison

The silica-supported chromate can be activated directly to a very efficient ethylene polymerization catalyst by ethylene itself or by reduction under CO, to yield active Cr(ll) bisiloxy species, ](=SiO)2Cr] [8]. While the silsesquioxane Cr derivative on its own does not lead to an active polymerization catalyst under ethylene (albeit only low ethylene pressure were tested), the silsesquioxane chromate ester can yield an active polymerization catalyst by addition of methyl-aluminoxane as co-catalyst. Comparison between the two catalytic systems is therefore possible but suffers from the lack of molecular definition of the active homogeneous species obtained after activation with the alkylating agent (Scheme 14.11). 

Vogel, E. and Natarajan, A.T. The relation between reaction kinetics and mutagenic action of monofunctional alkylating agents in higher eukaryotic systems Interspecies comparisons. IN deSerres, F.J. and Hollaender, A., eds. Chemical Mutagens Principles and Methods for Their Detection, Volume 7. New York Plenum Press. 1982. p. 295-336. 

This facile preparation is suitable for preparation of larger amounts of salt Like triethyloxonium fluoborate,2 trimethyloxonium fluoborate is a potent alkylating agent. In comparison with trimethyloxonium 2,4,6-trinitrobenzenesulfonate,5trimethyl-oxonium fluoborate is easier to make but does not keep quite as well on storage. 

As it can be seen, the oxo group in 142 was inactive while the thioxo group at C-3 was very reactive. Formation of pyrazoles in the oxo compound was explained by the reactivity of C-6. When triazepine 141 was treated with 1 or 2 equiv of alkyl bromide, only 152 was obtained but when a large extent of the alkylating agent was used, a small amount of the dialkylated 150 was formed. The different reactivity of 141 and 142 was explained by a softer basic character of the thioxo group in comparison with the oxo group. 

Figure 13.7. Some alkylating agents and their reactions with DNA. a The N-mustard (di-[chloroethyl]-amine) group is found in several agents such as mechlorethamine and cyclophosphamide. b Successive reaction of the N-mustard group with two guanine bases, potentially forming a cross-link between the two strands of a DNA molecule, c Tautomerisation of guanine, after alkylation of its N7 position. Adenosine (bottom left) is shown for comparison.

Gichner, T., Ptacek, O., Stavreva, D.A. and Plewa, M.J. (1999) Comparison of DNA damage in plants as measured by single cell gel electrophoresis and somatic leaf mutations induced by monofunctional alkylating agents. Environmental and Molecular Mutagenesis, 33, 279-286. 

Comparisons of alkyl sulphonates with other powerful alkylating agents... 

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