Preparation of the Diels-Alder adducts of methyl vinyl sulfone and cyclopentadiene and of their dihydro derivatives

Philips, J. Christopher; Oku, Masayoshi

doi:10.1021/jo00799a048

Cited by 11 publications

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“…Compound 1 was synthesized as described by Chung et al Compound 2 was made by hydrogenation of commercially available 2-phenyl-2-norbornene . The synthesis of 3 was achieved by a Diels–Alder reaction of cyclopentadiene with methyl vinyl sulfone, followed by catalytic hydrogenation . The resulting 2-endo-methanesulfonylnorbornane was then reduced to the thioether 3 and purified by column chromatography …”

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Spectroscopic Evidence for a New Type of Bonding between a Thioether Radical Cation and a Phenyl Group

et al. 2013

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The oxidation potential of thioethers constrained to be near aromatic rings is lowered, due to an antibonding interaction between the p-type sulfur lone pair with the neighboring phenyl π-system which on removal of an electron becomes a new kind of 3-electron S\π bonding that reveals itself in the photoelectron spectrum and by an electronic transition involving the orbitals participating in the S\π bond.Methionine is one of the most easily oxidized amino acids, and its thioether functional group has a high susceptibility to be attacked by free radicals. 1 It has been suggested to play a role in the pathogenesis of neurodegenerative diseases such as Parkinson's 2 and Alzheimer's 3 disease. Also, methionine has been postulated to be involved in long-range electron transfer through proteins using a multistep hopping process, 4 a process that is, however, not thermodynamically feasible unless the incipient thioether radical cations are stabilized by some neighboring moieties.An unusual property of the radical cations of dialkyl sulfides is their propensity to form two-center, threeelectron bonds with the nonbonding electrons of the neutral precursor, or with those of another heteroatom 5 (X in Scheme 1, left side). Such complexes distinguish themselves by broad σfσ* absorption bands which usually lie in the visible range. 5a Using model compounds where a methylthio and an amide moiety are attached to a norbornane skeleton, it was shown that such [S\X] complexation leads indeed to a decrease of the oxidation potential of the thioether, 6 as shown in Scheme 1. Hence, such interaction may account for the enhanced rate of electron transfer in model peptides where such interactions are possible.This paper provides experimental evidence that this propensity of sulfur radical cations to stabilize themselves by interacting with neighboring lone pairs can be extended † The University of Fribourg. ‡ The University of Arizona.(1) (a) Vogt, W. Free Radical Biol. Med. 1995, 18, 93-105. (b) Bobrowski, K.; Houee-Levin, C.; Marciniak, B. Chimia 2008, 62, 728-734. (2) Wassef, R.; Haenold, R.; Hansel, A.; Brot, N.; Heinemann, S. H.; Hoshi, T.

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Spectroscopic Evidence for a New Type of Bonding between a Thioether Radical Cation and a Phenyl Group

et al. 2013

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“…However, there are many reports of hydrogen–deuterium exchange of sulfones under basic conditions (e.g. NaOD, D 2 O, reflux) 17–22…”

Section: Resultsmentioning

confidence: 99%

Unusual base‐catalyzed exchange in the synthesis of deuterated PF‐2413873a

Rozze

Fray

2009

Labelled Comp Radiopharmac

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The preparation of deuterated PF-2413873 (4-[3-cyclopropyl-1-(methanesulfonylmethyl)-5-methyl-1H-pyrazol-4-yl]oxy-2, 6-dimethylbenzonitrile, 1) is described for use as a bioanalytical standard in clinical trials. Two strategies were investigated. The sulfone-containing substituent was labelled by base-catalyzed exchange, but unacceptable deuterium loss was noted under assay conditions. Alternatively, labelling 4-cyano-3,5-dimethylphenol was achieved by heating with deuterium oxide over platinum oxide. After building up the pyrazole ring we discovered that, during the subsequent alkylation to attach the methylthiomethyl group, the base, potassium t-butoxide, caused unwanted scrambling of deuteriums on the aromatic portion and the methylthiomethyl group. Thus, it was necessary to remove all base-labile hydrogens to prevent their exchange. This was accomplished by alkylating the pyrazole with per-deuterated chloromethyl methylsulfide, oxidation to the sulfone, and selective removal of its deuteriums by treatment with sodium hydroxide. The unusual sensitivity and selectivity of these base-promoted exchange reactions are discussed. Thus,

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“…By the usual method, the alcohol 12a was converted to the acetate 13a3a'n [95% with acetic anhydride and pyridine; mp 176-178°; ^1' 1.89 (3 H, s), 2.08 (3 H, s), 3.24 (3 H, s), 3.77 (3 H, s), 3.90 (3 H, s), 3.94 (3 H, s), and 4.00 (3 H, s)] which was oxidized with iodosobenzene diacetate in acetonitrile containing dimethyl sulfide, to afford the cyclized diacetate 14a3b'n [amorphous solid; M+ (found) 677.1288 and 679.1266, (cald) 677.1268 and 679.1239; °°£13 (1.2 mg in 0.3 ml) 1.63 (3 H, s), 1.95 (3 H, s), 2.01 (3 H, s), 3.02 (3 H, s), 3.51 (3 H, s), 3.80 (3 H, s), 3.86 (3 H, s), 3.87 (3 H, s)]12 in 30% yield.11•13 The two new asymmetric centers introduced in this step are expected to be desired ones for the steric reasons.…”

Section: Sirmentioning

confidence: 99%