9-Borabicyclo nonanes, 9-allyl

In contrast to ordinary chiral aldehydes (having no ability to be chelated), the reaction of 9-allyl-9-borabicyclo[3.3.1]nonane(allyl-9-BBN) with the corresponding chiral imines 4 produces the isomer syn-6 either exclusively or predominantly (Cram selectivity Table 8)5,6. The very high 1,2-asymmetric induction is explained by a six-membered. chair-like transition state, in which the inline R group occupies an axial position due to the stereoelectronic effect of imines (R CH = NR). 

Bromo-9-borabicyclo[3.3.0]nonane (9-Br-BBN), CH2CI2, reflux, 87-100% yield.9-Br-BBN also cleaves dialkyl ethers, allyl aryl ethers, and methylenedioxy groups. 

The silicon- and sulfur-substituted 9-allyl-9-borabicyclo[3.3.1]nonane 2 is similarly prepared via the hydroboration of l-phenylthio-l-trimethylsilyl-l,2-propadiene with 9-borabicy-clo[3.3.1]nonane36. The stereochemistry indicated for the allylborane is most likely the result of thermodynamic control, since this reagent should be unstable with respect to reversible 1,3-borotropic shifts. Products of the reactions of 2 and aldehydes are easily converted inlo 2-phenylthio-l,3-butadienes via acid- or base-catalyzed Peterson eliminations. 

The results show that modest chelation control can be obtained using organomctallics like allylmagnesium chloride, chloromagnesium allyltriethylaluminate and allylzinc bromide, which are capable of /1-chelation. In contrast to this, 9-allyl-9-borabicyclo[3.3.1]nonane (9-allyl-BBN)... 

From a- or 0- substituted aldehydes or ketones by elimination reactions Benzeneselenenyl trichloride, 27 Methanesulfonyl chloride-4-Di-methylaminopyridine, 176 9-(Phenylseleno)-9-borabicyclo-[3.3.1]nonane, 245 By oxidation of allylic substrates Pyridinium chlorochromate-Benzo-triazole, 262 By other methods Alumina, 14... 

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-... 

Related Reagents. fi-Allyl-9-borabicyclo[3.3.1-nonane B-Allyldiisocaranylborane fi-Allyldiisopinocampheylborane B-Crotyldiisopinocampheylborane (f ,f )-2,5-Dimethylborolane. 

Suzuki couplings. Pd-catalyzed reactions of B-allyl borate complex derived from 6-methoxy-9-borabicyclo[3.3.1]nonane with aryl triflates give allylarenes. This technique broadens the scope of the Suzuki coupling to allow transfer of Me, TMSCHj, and alkynyl groups which has eluded conventional manipulations. 

Trimethylsilylacetonitrile, 427-428 7-Trimethylsilyl alcohols, 51 Trimethylsilylalkynes, 126 Trimethylsilylallene, 428-429 a-T i iniethylsilylallenes. 433-434 [(Trimethylsilyl)allyll lithium, 430 a-Trimethylsilylcrotyl-9-borabicyclo[3.3.1) nonane, 430-431... 

Hydroboration of an allylic chloride gave a cyclopropane 14 when the intermediate or-ganoborane was treated with aqueous sodium hydroxide. 9-Borabicyclo[3.3.1]nonane is particularly suitable the geometry present in the alkene is retained in the product. 3-Bromopropyne underwent reaction with two equivalents of 9-borabicyclo[3.3.1]nonane, subsequent treatment with methyllithium and then with hydrogen peroxide gave cyclopropanol. 

Both difficulties are resolved by use of B-(y-chloropropyl)-9-borabicyclo[3.3.1] nonanes, available by the reaction of 9-BBN with an allylic chloride.8... 

NaBH4-CeCl3,6H20-Me0H like the parent 9-BBN, B-(l,2-dimethyl-propyl)-9-borabicyclo[3,3,l]nonane also produces allylic alcohols exclusively from o ,/3-enals e.g. citral). The full paper on the exclusive reduction of the... 

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