(E)-2-boryl-1,3-butadiene derivatives of the 10-TMS-9-BBDs: highly selective reagents for the asymmetric synthesis of anti-1,2-disubstituted 3,4-pentadien-1-ols.
The efficient stepwise construction of optically pure trans-4-substituted 2-boryl-1,3-butadienes 6 is described. Hydroboration of 1-alkynes with either enantiomeric form of 3 leads to the pure trans-1-alkenylboranes 4 which undergo addition of alpha-ethoxyvinyllithium followed by a BF(3)-mediated 1,2-B-->C vinylic group migration to provide 6. These organoboranes 6 serve as a new type of asymmetric allylborating agent providing an extremely selective protocol for the preparation of anti-1,2-disubstituted 3,4-pentadien-1-ols 8 as essentially single diastereomers in enantiomerically pure form. One example of a cis-2-boryl-1,3-butadiene (9) was prepared through a Grignard procedure. It was found to provide the corresponding syn-alcohol 11. The utility of 8 was demonstrated in their conversion to substituted beta-hydroxy acids 12 through ozonolysis and to substituted alpha,beta-unsaturated-delta-lactones 13 through Ru-catalyzed cyclocarbonylation.
González
Javier R
JR
University of Puerto Rico, Department of Chemistry, Rio Piedras, PR.
González
Ana Z
AZ
Soderquist
John A
JA
D001896:Boron Compounds / Q000737:chemistry*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry*; D002070:Butadienes / Q000138:chemical synthesis* / Q000737:chemistry; D008968:Molecular Conformation; D020005:Propanols / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D001896:Boron Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002070:Butadienes; D020005:Propanols