Roush allylboronation synthesis

A number of applications in the synthesis of complex structures have been documented. The versatility of the Roush allylboron reagents is demonstrated in the diverse range of substrates that have been successfully employed. In a formal total synthesis of ikarugamycin, the diene in 31 was protected as the iron complex, and the aldehyde in 31 underwent crotylation to afford 33 in 98% ee (Equation 5) [63]. 

Hunt and Roush <1995TL501> achieved a synthesis of swansonine 230 via a stereoselective allylation of a silyl allylboronate derived from tartaric acid followed by a Tamao-Fleming oxidation to introduce the C-2 hydroxy functionality (Scheme 54). 

The total synthesis of the 20-membered macrolide (+)-lasonolide-A was undertaken by S.H. Kang and co-workers. During the construction of the C15-C25 subunit, they utilized the Roush asymmetric allylation reaction to introduce the C21 and C23 stereocenters. First, (R,R)-diisopropyltartrate derived allylboronate was used to provide the (S)-homoallylic alcohol with 78% ee. A second asymmetric allylation was achieved utilizing the (S,S)-diisopropyltartrate-derived allylboronate to form the (R)-homoallylic alcohol with a 91% ee. 

Roush, W. R., Grover, P. T. Diisopropyl tartrate (E)-Y-(dimethylphenylsilyl)allylboronate, a chiral allylic alcohol 3-carbanion equivalent for the enantioselective synthesis of 2-butene-1,4-diols from aldehydes. Tetrahedron Lett. 1990, 31,7567-7570. 

The synthesis and use of tartrate-modified allylboronate 1 was first reported by Roush and co-workers in 1985. The synthesis and use of the corresponding (E)- and (. -crotylboronate reagents 2 and 3 was published by Roush and co-workers shortly thereafter. The ease of synthesis, stability and efficient reactivity of these reagents offers advantages over many other allyl- and crotylmetal reagents. Roush and co-workers have extensively explored the enantioselective allylations with achiral aldehydes as well as the... 

The allylboronate reagent 1 was used twice in the synthesis of (-)-lasubine I by Wang and Liao. (-)-Lasubine I (67) is a bioactive alkaloid isolated from the Lythraceae plant.(-)-Lasubine I contains three stereocenters in a quinolizidine core. Roush allylation of aldehyde 63 with provided the 1,3-aminoalcohol 67 in > 90 < 10 diastereoselectivity. Alcohol protection and alkene oxidation provided an intermediate aldehyde which underwent Roush allylation with to provide homoallylic... 

Roush has crafted a class of allyl/vinyl diboron reagents that participate in sequential aldehyde addition 1,5-anti-diols reactions and enable the expeditious synthesis of 1,5-diols. The hydroboration reaction of allene 34 furnishes 35, treatment of which with aldehydes results in the formation of 36 (Scheme 5.6) [64]. These allylboronate adducts subsequently undergo addition to a second set of aldehydes, generating 1,5-anti-diols 37 with high diastereoselectivity (S 20 1) and optical purity (S 89% ee). Use of the bulkier boronate 38 gives 1,5-syn-diols 39 with equally high stereoselectivity (dr >14 1, ee>91%) [65]. 

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