Simple, efficient, and modular syntheses of polyene natural products via iterative cross-coupling.

Materials. Pd(PPh3)4 was a generous gift from Sigma-Aldrich. Commercial reagents were purchased from Sigma-Aldrich, Strem, Fisher Scientific, Alfa Aesar, or Lancaster Synthesis and were used without further purification unless otherwise noted. Solvents were purified via passage through packed columns as described by Pangborn and coworkers (THF, Et2O, CH3CN, CH2Cl2: dry neutral alumina; hexane, benzene, and toluene: dry neutral alumina and Q5 reactant; DMSO, DMF: activated molecular sieves). Triethylamine and 2,6-lutidine were freshly distilled under an atmosphere of nitrogen from CaH2. The following compounds were prepared according to literature precedent: (E)-(2bromoethenyl)dibromoborane (3), (E)-1-chloro-2-iodoethylene (17), (1E,3E)-2-methyl-4-(2,6,6trimethylcyclohex-1-enyl)buta-1,3-dienylboronic acid (19), (E)-3-bromobut-2-enal (21), (E)-2(tributylstannyl)vinylzinc chloride (15), (E)-methyl 10-iododec-9-enoate (34), diol (37), dichlomethylpinacolboronic ester (42) .