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Roush Allylation
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The Roush Asymmetric Allylation allows the enantioselective synthesis of homoallylic alcohols from the reaction of allylboronates with aldehydes. • General features: • 1. The preparation of allylboronates may be achieved by esterification of allylboronic acid or by transesterification of triisopropylallylboronate. • 2. The reaction is typically carried out in toluene, in the presence of 4Å molecular sieves at low temperatures: -78 °C. • 3. Selecting the proper boronate gives access to one enantiomer of the homoallylic alcohol product or the other. • 4. (E)- crotylboronate derivatives lead to the formation of the anti-diastereomer, while (Z)- crotylboronates give the syn product. Also, (E)-crotylboronates usually exhibit higher enantioselectivities than (Z)- crotylboronates. • Seminal publications: • 1. Roush, W. R., Walts, A. E., Hoong, L. K., J. Am. Chem. Soc. 1985, 107, 8186-8190. https://doi.org/10.1021/ja00312a062 • 2. Roush, W. R., Ando, K., Powers, D. B., Halterman, R. L., Palkowitz, A. D., Tetrahedron Lett. 1988, 29, 5579-5582. https://doi.org/10.1021/jo01266a061 • 3. Roush, W. R., Grover, P. T., Lin, X., Tetrahedron Lett. 1990, 31, 7563-7566. • 4. Roush, W. R., Grover, P. T., Tetrahedron Lett. 1990, 31, 7567-7570. • References: • NROChemistry: https://nrochemistry.com/roush-asymme...
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