An Unusual Route to Deoxysugars by Hydrogen Atom Transfer from Cyclohexane. Possible Manifestation of Polar Effects in a Radical Process

The xanthate route to organofluorine derivatives. A brief account

“…We found that adduct 148 derived by addition of xanthate 146 to heptadecafluorodecene could be reduced into 150 by simply heating to reflux in cyclohexane in the presence of a very small amount (ca 5 mol%) of peroxide (Scheme 34). 64 The same reduction could not be accomplished on the non-fluorinated analogue 147 and hardly any nitrile 149 could be observed under the same conditions.…”

Syntheses of Organofluorine Derivatives by a New Radical Process

“…We found that a simple, yet highly efficient reductive method existed, which took advantage of the electrophilic character of a radical centre adjacent to inductively acting (-I) electron withdrawing groups, and especially fluorine atoms. Reduction of compound 21, obtained by radical addition of acetonitrile derived xanthate 19 to heptadecafluorodecene, is a case in point (9). The xanthate is simply dissolved in refluxing cyclohexane and treated with a small amount of lauroyl peroxide.…”

Hydrosulfonylation Reaction with Arenesulfonyl Chlorides and Tetrahydrofuran: Conversion of Terminal Alkynes into Cyclopentylmethyl Sulfones

“…[12] We report herein ah ydrosulfonylation procedure based on the use of commercially or readily available arenesulfonyl chlorides and THF as the source of the hydrogen atom, thus avoiding the use of any dedicated reducing agent. [18] Rapid solvent screening showed that weak-hydrogenatom-donor solvents,such as benzene,acetonitrile,and ethyl acetate,a lso provided the cyclizedp roduct 2a but in lower yields (Table 1, entries 2-4). [13,14] Ther eaction was observed for the first time during an attempt to form ac yclopentane derivative through chlorosulfonylation of alkyne 1a with para-toluenesulfonyl chloride and dilauroyl peroxide (DLP) in cyclohexane at reflux (Scheme 2).…”

“…Theresults confirmed that the ratio of cyclic/acyclic products is determined during the translocation step and not during the subsequent very fast cyclization. [18] This key step is strongly facilitated by polar effects. On the basis of these observations,wepropose the mechanism depicted in Scheme 6.…”

“…80 66 2b enzene 80 40 3a cetonitrile 82 19 4e thyl acetate 77 32 51 ,4-dioxane 101 68 6t etrahydrofuran 66 81 [a] Reaction conditions: 1a (1 mmol), p-toluenesulfonyl chloride (2 equiv), dilauryl peroxide (DLP;0 .5 equiv). [18,29] Finally,t he nucleophilic 2-tetrahydrofuranyl radical is rapidly chlorinated by ArSO 2 Cl owing to favorable polar effects. Thes tarting electrophilic sulfonyl radical adds efficiently to the terminal alkyne to furnish ah ighly reactive alkenyl radical that is perfectly suitable to abstract ahydrogen atom from an aliphatic CÀHbond.…”