Malonic acid derivatives, oxidative dimerization

Compounds containing active hydrogen atoms (pK = 11-25) could be brominated when DBU was added dropwise into a mixture of substrate (phenylacetylene, diethyl butylmalonate, indene, or fluorene) and BrCClj in benzene (78CL73). Compounds with lower acidity (pK 29) exhibited no reaction. With more acidic derivatives (diethyl malonate and benzyl cyanide), oxidative dimerization also occurred. Oxidative dimerization also took place when BrCClj was added dropwise into a solution of active methylene compound and DBU in benzene. The ratio of the reaction products depended on the ratio of DBU and BrCCIj. 

Tetrathianes. (1) Oxidative dimerization of a,a-disuhstituted alkanedithioic acid dianions (Scheme 38) or 1,1-dithiols (Equation 17) - very limited examples and a-monosuhstituted alkanedithioic acids decompose (2) reductive or pyrolytic dimerization of gi OT-disulfenyl dichlorides (Equation 18) - only malonate-derived examples (3) reaction of a-chloro sulfenyl chlorides with sodium trithiocarhonate (Equation 19) - only malonate-derived examples (4) sodium thiophenoxide-catalyzed reaction of thioketones with elemental sulfur (5) reaction of benzo-furan-3(2//)-one with S2CI2" (6) UV irradiation of a CS2 solution of a diazirine (7) reaction of a 2,2,4-trisubstituted-1,3-dithietane with Oxone (Scheme 54)". Method (4) is the most convenient and general of these. 

For the preparation of long chain alkanes from fatty acids it is useful to extract the electrolyte contin-ously with a high-boiling nonpolar solvent, e.g. 2-methylheptane. Cyclopropanecarboxylic acids in some cases have been dimerized, e.g. or (15) in other cases the radical is further oxidized to a carbocation which then undergoes ring opening and solvoiysis to allylic compounds. Specifically substituted 1,2-diphenyiethanes have been prepared from phenylacetic acids (Table 2, entries 22 and 23). A variety of 2,3-disubstituted succinic acids and their derivatives have become accessible from malonic... 

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