Polyenes Suzuki coupling reactions

This group of natural compounds is also structurally diverse ranging from the simple dienes like a sex pheromone (4E,7Z)-4,7-tridecadienyl acetate or ( )- , )-coriolic acid through typical polyenes like the all-trans-stereomer of ethyl retinoate to the more complex, optically active calyculins A and B. In the total syntheses of polyenes presented below, the structurally complex phosphonate or bisphosphonate reagents were used in the Horner-Wittig olefination reactions solely or in combination with the Suzuki coupling. 

Lera and coworkers successfully employed this thallium(i) hydroxide-aecelerated Suzuki reaction in the stereocontrolled polyene syntheses of retinol (vitamin A) and derivatives and polyenic alarm pheromones of cephalaspidean molluscs navenone A and haminol Despite some initial examples where thallium(i) ethoxide failed as an alternative for thallium(i) hydroxide there are an appreciable number of cases where thallium(i) ethoxide furnished great results. The first successful use of thallium(i) ethoxide was reported by Chamberlin and coworkers in the total synthesis of microcystin LA, a serine-threonine phosphatase inhibitor (Scheme 20.17). A few years after the synthesis of mieroeystin L, Roush and coworkers extended the use of thallium(i) ethoxide in Suzuki couplings for a range of boronic acids and halides. Simultaneously, Danishefslq and Chemler ... 

The MIDA-protected boronate esters developed by Burke and coworkers allow iterative Suzuki cross coupling reactions under mild conditions to give polyenes [64,65]. The MIDA-protected boronate esters are stable and easily handled, and deprotection occurs readily at room temperature under mild basic conditions to provide the corresponding boronic acids. 

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