Reinecke, Sebastian, Johnson, and Pyun pression, eq 6, may be written as v -(k2/Ki)h0 [CrVI][ RPNO], which agrees with the rate law reported for the oxidation of diphenylmethane in acetic acid.1 2345678 This indicates that the kinetic behavior is essentially the same in both the aqueous sulfuric and the acetic acid system. However, since the value of Ki presum-ably depends on the nature of the anions present,6 the equilibrium constants are not expected to be identical for the two solvent systems.

A new, convenient, and efficient synthesis of the very useful d-bromothiophenes by the metal amide catalyzed rearrangement of the readily available a isomers is reported.

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ChemInform Abstract Asymmetric hydroboration of prochiral olefins such as (I) and subsequent removal of the chiral auxiliary yields the optically active borinane (VI), which is converted into a mixture of the borabicyclo(4.2.1)nonane (VIIIa) and -(3.3.1)nonane (IXa). By this route, seven mixtures of isomeric, optically active borabicyclononanes such as (VIII) and (IX) are prepared; on thermal isomerization the more stable (4.2.1)isomers can be isolated without loss of optical purity. The mixtures react readily with α-halogenated esters, ketones and nitriles such as (X) to give the products (XI) with high optical purities. Since both (+)-and (-)-α-pinene are readily available as chiral auxiliaries, a simple procedure for the synthesis of optically active compounds is given. The use of sterically more hindered alkyl groups in the borabicyclononanes gives poor results.

Enolization of Thioesters by ChxzBC1/Et3N. A representative example of enolization of S-tert-butyl thioacetate is described as follows. To a stirred solution of ChxzBCl (1.2 mL, 5.5 "01) and EbN (0.77 mL, 5.5 "01) in CCl, (15 mL) cooled at 0 "C was added an internal standard, benzene (0.5 mmol), followed by the slow addition of S-tert-butyl thioacetate (0.78 mL, 5 mmol). The molarity of the solution was adjusted to 0.3 M. The reaction mixture was stirred for 1 h and worked up as described for ketones. Analysis of the olefinic proton by 'H NMR suggests >95% enolization.Enolization of &Keto Ester by ChxzBC1/Et3N. The enolization of ethyl acetoacetate is described as follows. To a stirred solution of ChxzBC1 (1.2 mL, 5.5 mmol) and EbN (0.77 mL, 5.5 mmol) in CC14 (15 mL) cooled at 0 "C was added an internal standard, benzene (0.5 mmol), followed by the slow addition of ethyl acetoacetate (0.64 mL, 5 m o l ) . The molarity of the solution was adjusted to 0.3 M. The reaction mixture was stirred for 1 h and worked up as described previously for ketones. Analysis by 'H NMR showed 94% enolization.General Procedure for the Aldolization with Benzaldehyde. To a solution of enolborinate in diethyl ether generated from 5 mmol of the carbonyl compound using ChxzBC1/EbN as described above was added benzaldehyde (0.51 mL, 5 mmol) dropwise at -78 "C, and the mixture was stirred for 2-3 h. Then the reaction mixture was allowed to warm up overnight slowly to attain the room temperature. (Later we discovered that the reaction is essentially complete in 2-3 h at -78 "C, so that the slow warmup to 25 O C is unneccessary. Both procedures give the same results.) Then 10 mL of methanol was added to dissolve the precipitate (EhNHCl), 1.7 mL of HzOZ (30%) was added at 0 "C, and the mixture was stirred for 5-6 h at 25 "C. The solvent was then removed by water aspirator and the reaction mixture was extracted with ether, washed with dilute HC1 and water, and dried over anhyd Na2S04. The solvent was removed and the 1992,57, 504-511 products were analyzed as such by lH NMR to determine the syn/anti ratio.In the case of carboxylic acids, after the aldolization, 5 mL of H,O waa added to the reaction mixture at 25 "C. and the reaulth &e was stirred for 30 min. The products were then extra& with aqueous NaHC03, neutralized with 20% HC1, extracted with ether, dried over anhyd NazS04, concentrated, and analyzed by 'H NMR. Acknowledgment. We gratefully acknowledge financial support from the United States Office of Naval Research, which made this research possible.Registry No.