Fig. 4. Synthesis route of the DA torsional springs.
a, b Synthesis of o-LBrPhDPP (5a) and m-LBrPhDPP (5b) with L = phenoxybutyl. c, d Incorporation of 5a and 5b into the polyphenylene matrix to o-DPP-PmmpP (6a) and m-DPP-PmmpP (6b). Reaction conditions: (i) diisopropylsuccinate, NaOt-Am, FeCl3, t-AmOH, 100 °C, 15 h; (ii) Me-p-Tos, K2CO3, DMF, 120 °C, 3 h; (iii) 4-bromobutylzinc bromide (in situ), Pd2(dba)3, SPhos, DMAc, 80 °C, 2 h; (iv) 4-bromophenol, K2CO3, DMF, 50 °C, 16 h; (v) Pd2(dba)3, SPhos, Aliquat 336, toluene/2 M K2CO3 (aq), 70 °C, 24 h.