Stereodirected Synthesis with Organoboranes

Synthesis of Stegobiol and Its Oxidation to Stegobinone, the Components of the Female-Produced Sex Pheromone of the Drugstore Beetle

“…When the TBS protective group of 16 was deprotected by treatment with hydrofluoric acid in acetonitrile, stegobiol (2) was obtained in 47% yield. Pure stegobiol was indeed crystalline as reported by Matteson et al [11] [12] [13] , although Kodama et al [2] and also ourselves [7] reported it to be oily. Finally we carefully examined the oxidation of stegobiol (2) to stegobinone (1) so as to find out the proper conditions to obtain 1 as crystals.…”

“…Unfortunately our base-catalyzed cyclization of B was capricious and difficult to reproduce. Oppolzer and Rodriguez therefore developed a more reliable titanium tetrachloride-catalyzed condensation [8] [9] [10] , and synthesized serricolole by cyclization of C. A totally new approach leading to 1 was reported in 1993 by Matteson et al [11] [12] [13] . They prepared D by their stereodirected use of organoboranes, and D afforded both stegobiol (2) and stegobinone (1) as crystals.…”

Synthesis of 1-Alkenylboronic Esters via Palladium-Catalyzed Cross-Coupling Reaction of Bis(pinacolato)diboron with 1-Alkenyl Halides and Triflates

“…The use of an insoluble base suspended in toluene can tolerate various functional groups in haloalkenes (entries 4-6). Although (E)-1-alkenylboronates have been synthesized by hydroboration of terminal alkynes and (Z)-derivatives by a two-step procedure from 1-halo-1-alkynes 11 , the coupling reaction of diboron provided an alternative and stereoselective method for synthesizing both isomers with high stereoselectivity over 99% (entries 7 and 8). 2,2-Disubstituted 1-alkenylboronate and cyclic 1-alkenylboronate were obtained from the corresponding bromides without any difficulty because the side-reactions observed in Eq.…”

Asymmetric hydrogenation of 1-phenylethenylboronic acid and esters for the synthesis of chiral organoboron compounds

“…Chiral organoboron compounds [1] are available from the hydroboration of internal alkenes with chiral hydroboration reagents including di(isopinocampheyl)borane [2], mono-isopinocampheylborane [2], and 2,5-dimethylboronane [3]. The discovery of the intramolecular S N 2 substitution reaction of chiral (α-haloalkyl)boronic esters with carbon-or hetero-nucleophiles has resulted in an additional and practical method of broad scope [4].…”