Pyridinium salts, photoinduced

Moreover, in situ polyurethane formation was performed by irradiation of the polymeric pyridinium salt in THF containing toluene diisocyanate and catalyst. It is clear that alkoxy pyridinium terminated polymers are useful materials as precursors for block copolymers and hydroxy functional telechelics. The latter are particularly attractive in photoinduced polycondensation and in applications where hydroxyl groups are needed to be protected. 

Cationic Systems Photoinduced cationic polymerization can be initiated directly or indirectly upon exposure to U V light in the presence of onium or pyridinium salts with suitable nucleophilic counterions [33], These initiating systems have been employed in synthesizing block and graft copolymers [34], For example, side-chain benzoin-containing polymers were used as promoters to yield poly(benzoin acrylate-g-cyclohexene oxide) copolymers [35] by using iV-ethoxy-2-methyl-pyridinium... 

The pyridinium salt end-functionalized PTHFs can be used as polymeric initiators for photoinduced reactions. Upon photolysis the pyrdinium moiety decomposes and polymeric radicals are formed. Depending on the additives present in the system, hydroxy telechelics (305) or block copolymers (302) are thus formed. 

Despite considerable efforts, the formulation in equation (42) remains incomplete owing to the high reactivity of organocuprates as well as their oligomeric nature. Accordingly, we select organoborates as stable electron donors to study alkyl additions to various pyridinium acceptors (by thermal and photoinduced electron transfer) via charge-transfer salts as follows. 

Zhu, D. and Kochi, J.K., Alkylation of pyridinium acceptors via thermal and photoinduced electron transfer in charge-transfer salts with organoborates, Organometallics, 18,161, 1999. 

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