67760-89-8Relevant academic research and scientific papers
Bidirectional Asymmetric Allylboration. A Convenient Asymmetric Synthesis of C2-Symmetric 3-Methylenepentane-1,5-diols and Rapid Access to C2-Symmetric Spiroketals
Barrett, Anthony G. M.,Braddock, D. Christopher,de Koning, Pieter D.,White, Andrew J. P.,Williams, David J.
, p. 375 - 380 (2007/10/03)
The double allylboration of aldehydes using 1,3-bis(diisopinocampheylboryl)-2-methylenepropanes (R,R)-3 and (S,S)-3 under Brown's salt-free conditions provides C2-symmetric 3-methylenepentane-1,5-diols 1 in excellent enantiomeric excess. The absolute stereochemistry of the products was confirmed by a single-crystal X-ray study of bis-Mosher ester 6g. Desymmetrization and further functionalization of diol 1a were achieved by treatment of the bis-BOC carbonate 13 with IBr in toluene at -80°C to give cyclic iodocarbonate 14 as a single diastereomer. This methodology is also applicable in natural product synthesis; enantiomerically pure spiroketals 1,7-dioxaspiro[5.5]-undecanes 18 and 25, the latter representing an expedient synthesis of the AB ring system of the spongistatins 20, were easily accessed from simple starting materials in excellent yields and selectivities.
Chiral Synthesis via Organoboranes. 5. Asymmetric Allylboration via Chiral Allyldialkylboranes. Synthesis of Homoallylic Alcohols with Exceptionally High Enantiomeric Excess
Jadhav, Prabhakar K.,Bhat, Krishna S.,Perumal, P. Thirumalai,Brown, Herbert C.
, p. 432 - 439 (2007/10/02)
Allyldiisopinocampheylborane, prepared readily by treatment of methoxydiisopinocampheylborane with allylmagnesium bromide, adds smoothly to aldehydes with remarkable enantioselectivity, transferring an allyl group to the carbonyl carbon with boron going to the oxygen.The enantioselectivity in allylboration varies with the reaction temperature, increasing considerably by decreasing the temperature from 0 deg C to -78 deg C.However, the enantioselectivity achieved does not vary significantly with the structure of the aldehyde.The enantioselectivity in the condensation of the reagent with representative ketones is less favorable, but in selected cases the results are promising (as high as 75percent ee).Condensation of methallyldiisopinocampheylborane and (3,3-dimethyl-allyl)diisopinocampheylborane with aldehydes proceeds with equally high asymmetric induction, indicating that wide variation in the structure of the allylic moiety can be accommodated.The effect of changes in the chiral ligand on boron has also been studied.
ASYMMETRIC METHALLYLBORATION OF PROCHIRAL ALDEHYDES WITH METHALLYLDIISO-PINOCAMPHEYLBORANE. SYNTHESIS OF 2-METHYL-1-ALKEN-1-OLS IN 90percent ENAN-TIOMERIC PURITIES
Brown, Herbert C.,Jadhav, Prabhakar K.,Perumal, P. Thirumalai
, p. 5111 - 5114 (2007/10/02)
Methallyldiisopinocampheylborane, on condensation with aldehydes, provides 2-methyl-1-alken-4-ols in 90percent enantiomeric purities.
