173398-01-1Relevant academic research and scientific papers
Asymmetric Synthesis of 1,3-Butadienyl-2-carbinols by the Homoallenylboration of Aldehydes with a Chiral Phosphoric Acid Catalyst
Huang, Yiyong,Yang, Xing,Lv, Zongchao,Cai, Chen,Kai, Cheng,Pei, Yong,Feng, Yu
supporting information, p. 7299 - 7302 (2015/06/30)
Asymmetric C(sp)-C(sp2) bond formation to give enantiomerically enriched 1,3-butadienyl-2-carbinols occurred through a homoallenylboration reaction between a 2,3-dienylboronic ester and aldehydes under the catalysis of a chiral phosphoric acid (CPA). A diverse range of enantiomerically enriched butadiene-substituted secondary alcohols with aryl, heterocyclic, and aliphatic substituents were synthesized in very high yield with high enantioselectivity. Preliminary density functional theory (DFT) calculations suggest that the reaction proceeds via a cyclic six-membered chairlike transition state with essential hydrogen-bond activation in the allene reagent. The catalytic reaction was amenable to the gram-scale synthesis of a chiral alkyl butadienyl adduct, which was converted into an interesting optically pure compound bearing a benzo-fused spirocyclic cyclopentenone framework.
Asymmetrie synthesis of (1,3-butadien-2-yl)methanols from aldehydes via [1-(Silylmethyl)allenyl]methanols
Duran-Galvan, Maria,Connell, Brian T.
supporting information; experimental part, p. 2445 - 2448 (2010/09/03)
[1-(Silylmethyl)allenyl]methanols 2 were efficiently synthesized from aldehydes and (4-bromobut-2-ynyl)trimethylsilane in the presence of a catalytic amount of CrCl2 and tridentate carbazole ligands. The desired compounds were obtained with good yields (43-88%) and enantioselectivities (55-78% ee). Alcohols 2 may be treated with TBAF or 2 M HCl in the case of aliphatic substrates, to provide (1, 3-butadien-2-yl)methanols 3 in 43-81% yields. This method allows the synthesis of dienes 3 with no regioselectivity problems, and it tolerates a large number of functionalities.
Chiral Synthesis via Organoboranes. 44. Racemic and Diastereo- and Enantioselective Homoallenylboration Using Dialkyl 2,3-Butadien-1-ylboronate Reagents. Another Novel Application of the Tandem Homologation-Allylboration Strategy
Ramachandran, P. Veeraraghavan,Li, Guisheng,Brown, Herbert C.
, p. 100 - 104 (2007/10/03)
A highly general and efficient racemic and diastereo- and enantioselective homoallenylboration has been achieved with a novel boron reagent, dialkyl 2,3-butadien-1-ylboronate (dialkyl homoallenylboronate).The starting isopropyl 2,3-butadien-1-ylboronate is prepared from allenylmagnesium bromide and diisopropyl (halomethyl)boronate.This β,γ-unsaturated boronate reagent reacts readily with aldehydes via usual allylic rearrangement to give the alkyl(1,3-butadien-2-yl)methanols in excellent yields.Among the solvents examined, toluene favored enhanced reaction rates.The reaction is relatively sensitive to steric effects, so that sterically hindered aldehydes react significantly slower.Generaly, the reactivities are moderately lower than those of the corresponding simple allylboronates, possibly due to the reduced HOMO electron density of the internal double bond.Also, the reagent exhibits a unique anti diastereoselectivity in reaction with α-chiral aldehydes in contrast to the syn selectivity observed with a corresponding organosilicon reagent.However, this anti selectivity is similar to that observed for the allylboration reactions.We have successfully extended this reaction to the first general synthesis of optically active alkyl(1,3-butadien-2-yl)methanol using chiral tartrate boronate reagents with diisopropyl tartrate (DIPT) and bis(2,4-dimethyl-3-pentyl) tartrate (DMPT) as the chiral modifiers.These reagents react with aldehydes even at -78 deg C, albeit slowly, and exhibit remarkable enantioselectivity with al classes of aldehydes examined with the exception of aromatic and α-alkoxy aldehydes.Again, while the selectivity parallels that of the corresponding allylboronate, the reactivities are lower.Also, the double asymmetric homoallenylboronation of 2,3-O-isopropylidene-D-glyceraldehyde using the DMPT modified boronate reagent gives an excellent 98.5percent anti selectivity in the matched case and a moderately lower value, 82percent syn selectivity, in the mismatched case.
Preparation of racemic and chiral alkyl (1,3-butadien-2-yl)methanol derivatives ut,ilizing 1-trimethylsilyl-2,3-butadiene as a diene source
Hatakeyama, Susumi,Sugawara, Kazutoshi,Kawamura, Mitsuhiro,Takano, Seiichi
, p. 4509 - 4512 (2007/10/02)
Ti(IV) chloride mediated reaction of 1-trimethylsilyl-2,3-butadiene with various aldehydes and acetals has been examined establishing an efficient method for the preparation of alkyl(1,3-butadien-2-yl)methanols. Application of this method to chiral acetal
