85116-37-6Relevant academic research and scientific papers
Kinetic analysis of the asymmetric amplification exhibited by B-chlorodiisopinocampheylborane
Moeder, Charles W.,Sowa Jr., John R.
, p. 317 - 324 (2004)
A quantitative investigation was undertaken to determine experimentally the relative reaction rates of the heterochiral and homochiral species of B-chlorodiisopinocampheylborane (Dip-Cl), a reagent that exhibits asymmetric amplification. Using the method of flooding to reduce the apparent second-order reaction to pseudo-first-order conditions, rate constants of 3.8 (±1.0) × 10-4 and 1.7 (±0.8) × 10-5 M -1 s-1 (at -15°C) were found for the homochiral and heterochiral species, respectively. The resulting relative reaction rate, the value of g in Kagan and co-workers' model, was 0.04 ± 0.03. Additional experiments were conducted to confirm this value. The deterioration of the chiral purity of the final product was simulated throughout reaction conversion and compared with actual values. Through minimization, a relative reaction rate (g) of 0.08 ± 0.04 was determined. Finally, using 8-hydroxyquinoline complexation, the change in isomeric ratio of the Dip-Cl remaining in the reaction solution was measured. The relative reaction rate (g) required to consume the isomers at the observed rate was determined as 0.08 ± 0.01. Thus, three independent methods have been used to determine the relative reaction rate (g) of the heterochiral to homochiral species with good agreement to give an average value of 0.07 ± 0.03. Copyright
Quantitative stereochemical analysis of a reagent that exhibits asymmetric amplification, B-chlorodiisopinocampheylborane (Dip-Cl)
Moeder, Charles W.,Whitener, Mark A.,Sowa Jr., John R.
, p. 7218 - 7225 (2000)
We show that complexation of B-chlorodiisopinocampheylborane (Dip-Cl) with 8-hydroxyquinoline results in an air- and moisture-stable complex. Using enantiomerically pure (+)-α-pinene, the (+,+)-Dip-quinoline complex, [(+)-C10H17]2B(η2- N,O-C10H6NO), was isolated and characterized by spectroscopic and crystallographic methods. When Dip-Cl is prepared from enantiomerically impure (+)-α-pinene a mixture of heterochiral, (+,-)-Dip-Cl, and homochiral, (+,+)-Dip-Cl and (-,-)-Dip-Cl, stereoisomers are formed. We have developed the 8-hydroxyquinoline complexation method for quantification of these stereoisomers by chiral HPLC. Since this is the first quantitative analysis of a reagent that exhibits asymmetric amplification, it enables us to verify part of Kagan's model for this phenomenon and evaluate the terms β and K which are measures of the relative amounts of stereoisomers. Our analysis shows that there is a preference for the formation of the heterochiral (+,-)-Dip-Cl isomer; therefore, the stereoisomers are not statistically distributed. This is beneficial for the asymmetric amplification process because it causes the heterochiral diastereomer to absorb the minor (-)-α-pinene enantiomer, thereby increasing the effective concentration of (+,+)-Dip-Cl that is formed from (+)-α-pinene. We also studied the distribution of stereoisomers as a function of the preparation temperature of the Dip-Cl reagent (0, 10, 20 °C). Increasing the preparation temperature increases the relative amounts of the homochiral stereoisomers, suggesting that the activation energy for the formation of the homochiral isomers is greater than for the heterochiral isomer. Thus, at higher preparation temperatures greater amounts of (-,-)-Dip-Cl are formed from (-)-α-pinene. However, there is a surprising benefit as higher levels of asymmetric induction are observed, especially when low enantiomeric purity α-pinene is used. In addition, the reduction reactions proceed slightly faster when Dip-Cl is prepared at higher temperature. In sum, the complexation of Dip-Cl with 8-hydroxyquinoline and subsequent analysis by chiral HPLC provides considerable insight into the asymmetric amplification process observed with this reagent. Moreover, we have shown how the conditions used for the preparation of the reagent affect the asymmetric amplification process.
Total Synthesis and Antitrypanosomal Activity of Janadolide and Simplified Analogues
Chung, Jonathan H.,Corcilius, Leo,Geraghty, Kieran,Kaiser, Marcel,Payne, Richard J.,Tang, Arthur H.
supporting information, (2020/04/20)
Janadolide is a cyclic depsipeptide natural product isolated from the marine cyanobacterium Okeania sp. Herein, we describe the total synthesis of janadolide, along with eight simplified analogues, via an efficient solid-phase strategy. Crucial to the synthesis of the natural product was the construction of a key polyketide fragment via an enantioselective (-)-B-chlorodiisopinocampheylborane-mediated reduction and a B-alkyl Suzuki reaction. Janadolide and the simplified analogues exhibited antitrypanosomal activity against pathogenic Trypanosoma brucei rhodesiense and Trypanosoma cruzi parasites.
Enantioselective total synthesis of the mexicanolides: Khayasin, proceranolide, and mexicanolide
Faber, Jonathan M.,Eger, Wilhelm A.,Williams, Craig M.
, p. 8913 - 8921 (2013/01/15)
The enantioselective total synthesis of the limonoids khayasin, proceranolide and mexicanolide was achieved via a convergent strategy utilizing a tactic aimed at incorporating natural products as advanced intermediates. This extended biomimetically inspir
A convenient and economical method for the preparation of DIP-chloride(TM) and its application in the asymmetric reduction of aralkyl ketones
Zhao, Mangzhu,King, Anthony O.,Larsen, Robert D.,Verhoeven, Thomas R.,Reider, Paul J.
, p. 2641 - 2644 (2007/10/03)
A convenient and economical in situ preparation of DIP-chloride(TM) from NaBH4, BCl3 and α-pinene is described. Its application in the asymmetric reduction of representative aralkyl ketones is presented.
Chiral Synthesis via Organoboranes. 14. Selective Reductions. 41. Diisopinocampheylchloroborane, an Exceptionally Efficient Chiral Reducing Agent
Brown, Herbert C.,Chandrasekharan, J.,Ramachandran, P. V.
, p. 1539 - 1546 (2007/10/02)
Diisopinocampheylchloroborane, readily prepared in both enantiomers in high chemical and optical purities (99percent ee) via hydroboration followed by treatment with dry hydrogen chloride in ethyl ether, reduces prochiral ketones at convenient rates in tetrahydrofuran at -25 deg C.Reduction of simple dialkyl ketones, 2-butanone, 2-octanone, and 3-methyl-2-butanone, yields the corresponding alcohols with 4percent, 7percent, and 32percent optical induction.On the other hand, aralkyl ketones are reduced with very high asymmetric induction.Thus, acetophenone, propiophenone, butyrophenone, and decanophenone are reduced with 98percent, 98percent, and 97percent ee, respectively.Branching of the alkyl chain diminishes the induction.Isobutyrophenone and pivalophenone are reduced in 78percent and 79 ee, respectively.Functional groups in the aromatic ring are not affected by the reagent and do not appear to influence significatly the optical yield realized.Thus, 2',5'-dimethoxypropiophenone is reduced in 96percent ee. 1-Indanone and α-tetralone are reduced in 98percent and 87percent ee, respectively. 2'-Acetonaphthone is reduced in 98percent ee.Heteroaryl alkyl ketones are also reduced with excellent optical induction.Thus, 3-acetylpyridine and 2-acetylthiophene are reduced in 92percent and 91percent ee, respectively.The reagent reduces α-tertiary aliphatic ketones under neat condition at room temperature with very high optical induction. 3,3-Dimethyl-2-butanone, ethyl 2,2-dimethylacetoacetate, 2,2-dimethylcyclopentanone, 2,2-dimethylcyclohexanone, and spirononan-1-one are reduced to the corresponding alcohols in 95percent, 84percent, 98percent, 91, and 95percent ee, respectively.Some α,β-unsaturated ketones are reduced with lesser optical induction, such as 4-phenyl-3-butyn-2-one and 2-cyclohexenone, which are reduced to the alcohols in 21 and 36percent ee respectively.On the other hand, trans-4-phenyl-3-buten-2-one is reduced to the alcohol.Certain α-keto esters are reduced in 50-70percent ee.The mechanism of the reduction is postulated to be via a six-membered cyclic "boatlike" transition state.X-ray crystal structure data for the reagent are presented.
Enantioselective Ring Cleavage of meso-Epoxides with B-Halodiisopinocampheylboranes
Joshi, N. N.,Srebnik, M.,Brown, Herbert C.
, p. 6246 - 6248 (2007/10/02)
Asymmetric synthesis starting from meso compounds is an increasingly important method for the preparation of optically active compound.We now report the synthesis of optically active 1,2-halohydrins using B-halodiisopinocampheylboranes, Ipc2BX (1a-c).
