Highly Efficient Synthesis of Linear Pyrrole Oligomers by Twofold Heck Reactions

The twofold Heck reaction of the vinylpyrroles 3 a and 3 b with the iodobenzenes 4 a–c led to the linear pyrrole oligomers 5, 6, and 7. The synthesis of both symmetrical and unsymmetrical oligomers, such as 10 a and 10 b, was also accomplished by a Heck reaction of 8 and 9 and by a Heck reaction of 3 a and 11 followed by a Wittig reaction and a second Heck reaction with 8. The pentacyclic oligomers 14 and 19 were prepared by a twofold Heck reaction of 13 with 4 and by a twofold Heck reaction of 15 with 16 followed by a Wittig reaction and a twofold Heck reaction with 8.