Scheme 1. Synthetic routes to sensitizers XW40 and XW41. Reaction conditions: (i) 6-bromo-1-hexene, K2CO3, DMF; (ii) TFA, DDQ, Et3N, CH2Cl2; (iii) NBS, CH2Cl2; (iv) Zn(OAc)2·2H2O, CH2Cl2, CH3OH; (v) 2nd generation Grubbs catalyst, CH2Cl2; (vi) 3-ethynyl-10-hexyl-7-(4-(hexyloxy)phenyl)-10H-phenothiazine, AsPh3, Pd2(dba)3, THF, Et3N; (vii) for 7a: methyl-4-ethynylbenzoate, Pd2(dba)3, AsPh3, Et3N, THF; for 7b: methyl 4-(7-ethynylbenzo[c][1,2,5]thiadiazol-4-yl)benzoate, Pd2(dba)3, AsPh3, Et3N, THF; and (viii) LiOH·H2O, THF, H2O.
