Double cycloisomerization as a novel and expeditious route to tricyclic heteroaromatic compounds: short and highly diastereoselective synthesis of (+/-)-tetraponerine T6

[reaction: see text] Cu-Assisted double cycloisomerization of bis-alkynylpyrimidines afforded the 5-6-5 tricyclic heteroaromatic skeleton. This transformation was used as a key step in the highly diastereoselective total synthesis of (+/-)-tetraponerine T6.