Methyl dithiobenzoates, preparation

Benzotrichloride added dropwise during 1-1.5 hrs. at ca. 60 under Ng to a mixture of KHS and KOH in abs. ethanol prepared from KOH and HgS, gently refluxed for 30 min., aq. chloracetic acid neutralized with NaHGOg added rapidly, the stirred mixture heated to boiling as rapidly as possible, refluxed 5 min., added to ice, stirred and slowly acidified with coned. HGl carboxy-methyl dithiobenzoate. Y 54-63%. F. Kurzer and A. Lawson, Org. Synth. 42, 100 (1962). 

Recent attempts to prepare 26 by RAFT, however, failed [153]. Double hydrophilic block copolymers of NIPAM and 23e [154], as well as of N,N-diethylacrylamide and 23b [155], were prepared with the CTA benzyl dithiobenzoate, and exhibit LCST and UCST behavior in water. The new polymer 51 is also part of amphiphiUc di- and triblock copolymers [152]. Diblock copolymers with poly(ethylene glycol) methyl ether acrylate, dimethylacry-lamide, or 4-vinylstyrene sulfonate are macrosurfactants with a switch-able hydrophobic block. Triblock copolymers containing additionally 4-vinylbenzoic acid differ in the nature of the hydrophilic part [152]. Near-monodisperse block copolymers of N,N-dimethacrylamide and 49a were synthesized in different ways via macro-CTAs of both monomers as the first step. Such sulfobetaine block polymers form aggregates in pure water but are molecularly dissolved after addition of salt [152,156,157]. 

Poly(N,N-dimethylacrylamide) with controlled MW, low values for M /Mn, and a high proportion of meso dyads (approx. 85%) was prepared using ATRP (methyl 2-chloropro-pionate/CuCl/MeeTREN) and RAFT (with cumyl dithiobenzoate transfer agent) in the presence of Y(OTf)3. These systems were used for the first one-pot synthesis of stereoblock copolymers by RP. Well-defined stereoblock copolymers, atactic-l -isotactic poly(N,N-dimethylacrylamides), were obtained by adding Y(OTf)3 to either an ongoing RAFT or ATRP polymerization, started in the absence of the Lewis acid. "... 

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