9-Vinyl-9-borabicyclo 3.3.1 nonane

As in the Negishi reaction, various alkylboron reagents have also been successfully coupled with electrophile partners. Suzuki et al. coupled 1-bromo-l-phenylthioethene with 9-[2-(3-cyclohexenyl)ethyl]-9-BBN (27), prepared by a simple addition of 9-borabicyclo[3.3.1]nonane (9-BBN) to 4-vinyl-1-hexene (26), to furnish 4-(3-cyclohexenyl)-2-phenylthio-1-butene (28) in good yield [36],... 

B-Alkenyl-9-borabicyclo(3,3,l)nonane (B-alkenyl-9-BBN) adds across the carbonyl group of a simple aldehyde to afford in good yields, the corresponding allylic alcohol S2). The reaction proceeds with complete retention of vinylic borane stereochemistry resulting in the /raw-disubstituted olefin linkage in the final product. The reac-... 

The combination of 1,2-hydroboration of double bond and 1,1-organoboration of triple bond of the corresponding vinyl(alkinyl)silanes 268 with 9-borabicyclo[3.3.1]nonane (9-BBN) affords in high yield the l-silacyclopent-2-enes 269 <2006APOC99>. 

Synthesis of B-[Z]-l-alkenyl-9-borabicyclo[3.3.1]nonanes, not available by hydro-boration, is achieved via vinylic organolithiums ... 

Stereoselective addition of B-Br across a terminal acetylene (haloboration) was first reported by Blackborow (66). Suzuki and coworkers examined the intermediate obtained from the haloboration of alkynes with B-bromo and 5-iodo-9-borabicyclo[3.3.1]nonanes for various organoborane reactions. Suzuki has reviewed the applications of haloboration for organic syntheses (67-69). A recent application involving the 1,4-addition of a halovinyl-9-BBN to methyl vinyl ketone (70) for the synthesis of a promising anti-cancer agent, 12,13-desoxyepothilone B due to Danishefsky and coworkers is shown in Figure 19 (77). 

The Suzuki-Miyaura reaction [26] is a very reliable method for connecting the building blocks. It was of interest to apply it to allylamines in that capacity. We found that hydroboration of the vinyl group can be reliably accomplished with 9-borabicyclo[3.3.1]nonane (9-BBN), even in the presence of further disubsti-tuted double bonds, and the subsequent Suzuki-Miyaura coupling works well [27]. Several targets were addressed with these key reactions [28]. An example is... 

TMS-alkynes are oxidized at the terminal carbon to carboxylic acids by hydroboration/oxidation (dicyclohexylborane/NaOH, H2O2). This does not work with TIPS-alkynes. Instead, TIPS-alkynes are cleanly monohydroborated at the internal carbon by 9-borabicyclo[3.3.1]nonane dimer to give (Z)- -borylvinyl-silanes. These can be oxidized in high yields to a-silyl ketones, or cross coupled with a bromide R Br (R = aryl, benzyl, dimethyl-vinyl) in the presence of NaOH and tetrakis(triphenylphos-phine)palladium(0) to give /3,/3-disubstituted vinylsilanes (Suzuki reaction eq 14). The same nucleophilic substituted vinylsilane can be added to an aromatic aldehyde to provide access to ( )-3-silyl allyl alcohols. ... 

Hydroboration. y,S-Unsaturated ketones can be synthesized in good yield from methyl vinyl ketone and 9-borabicyclo[3,3,l]nonane as illustrated in Scheme 39. The coupling of hydrobated olefins with silver ions has been extended to dienes. 

Polybutadiene-based polyols can also be reached by consecutive reaction of 1,2-vinyl PBD with 9-borabicyclo[3.3.1]nonane (9-BBN), leading to hydro-boration, and oxidation with H202/Na0H [141]. Direct bishydroxylation with osmium tetroxide or using permanganate as catalyst has been reported as unsuccessful [200]. 

Ishiyama T, Nishijima K, Miyaura N, Suzuki A. Palladium (O)-catalyzed thioboration of terminal alkynes with 9-(alkylthio)-9-borabicyclo[3.3.1]nonane derivatives stereoselective synthesis of vinyl sulfides via the thioboration-cross-coupling sequence. J. Am. Chem. Soc. 1993 115 7219-7225. 

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