Cycloaddition of Buⁿ₃P.CS₂: Formation of Extended bis- and tris-1,3-Dithiolanes and Dithiolane-Containing Polymers

Reaction of the tri-n-butylphosphine/carbon disulfide adduct 1 with norbornene and aromatic di- and trialdehydes gives the bis- and tris-dithiolanes 7-9 resulting from Wittig reaction of 2. In the same reaction, norbornadiene diester 10 reacts only on the unsubstituted double bond to give bisdithiolanes 11 and 12, while norbornadiene itself reacts on both double bonds to give novel dithiolane-containing polymers 13-15. In the bis-dithiolane 16 derived from reaction of 1, norbornene and phthalaldehyde, the groups interact leading to cyclisation so that only the spiroindane isomer 17 is obtained and its X-ray crystal structure is presented. In the reaction of 1, 10 and phthalaldehyde the initial product 21 can be observed but it similarly cyclises upon acid catalysis to afford 22. By treatment of 21 with HBF4 followed by Et3N the opposite stereoisomer 23 is mainly obtained in addition to 22. (C) 1997 Elsevier Science Ltd.