- Catalytic Asymmetric Preparation of Polyfunctional Protected 1,2-Diols and Epoxides
-
α-Trialkylsiloxy aldehydes 4a,b add functionalized diorganozincs in the presence of catalytic amounts of (1R,2R)-bis(trifluoromethanesulfonamido)cyclohexane (8 mol percent), affording protected 1,2-diols in 39-89percent yield and 70-94percent ee.The conversion of the monosilylated 1,2-diols to functionalized chiral epoxides has been demonstrated.
- Eisenberg, Christina,Knochel, Paul
-
-
Read Online
- The Configuration of Distaminolyne A is S: Quantitative Evaluation of Exciton Coupling Circular Dichroism of N, O- Bis-arenoyl-1-amino-2-alkanols
-
The 2S configuration of the marine natural product distaminolyne A was recently disputed based upon total synthesis, yet paradoxically supported by a second independent total synthesis from a different research group. We now verify the 2S configuration of
- Molinski, Tadeusz F.,Salib, Mariam N.,Pearce, A. Norrie,Copp, Brent R.
-
p. 1183 - 1189
(2019/05/02)
-
- Collaborative effect of Mn-porphyrin and mesoporous SBA-15 in the enantioselective epoxidation of olefins with oxygen
-
The rational design of heterogeneous, low cost transition metal complexes that can catalyze olefin with high enantioselectivity and activity has been a challenging goal for the synthetic chemist. In this study a chiral ion pair strategy was used for the synthesis of a biomimetic efficient manganese-tetrapyridylporphyrin (H2TPyP) catalyst for the asymmetric epoxidation of olefins with O2. Complex Mn-TPyP was covalently linked to mesoporous SBA-15 in heme-type environments and its counter ion was replaced by L-tartrate anion (SBA15-[Mn(TPyP)TA]). Chiral and achiral homogeneous analogous of Mn-TPyP were also prepared. The Mn-porphyrin confined in nanoreactors of SBA-15 exhibited enhanced activity (TOF = 652 h?1) and enantiomeric excess (ee 93%) compared with the value obtained when the same chiral catalyst functioned in homogeneous solution (TOF 97 h?1 and ee 83%) in the oxidation of 1-decene with O2/isobutyraldehyde. The high specific surface area, uniformly sized pore channels and site isolated active centers of the catalyst may contribute to the high activity and enantioselectivity. SBA15-[Mn(TPyP)TA] was structurally stable and could be recycled for repeated use. Total turnover number in the oxidation of styrene after five cycles was 47,400 with 86% epoxide selectivity and ee 86%.
- Berijani, Kayhaneh,Hosseini-Monfared, Hassan
-
p. 113 - 120
(2017/11/10)
-
- A heterogenized chiral imino indanol complex of manganese as an efficient catalyst for aerobic epoxidation of olefins
-
Herein, a new heterogenized chiral catalyst, GFC-[Mn(L)(OH)], was synthesized by grafting the complex [Mn(L)(OH)] on carbon-coated magnetic Fe3O4 nanoparticle-decorated reduced graphene oxide sheets (GFC) through an amine linkage (L = (1R,2S)-1-(N-salicylideneamino)-2-indanol). The catalyst was characterized via FT-IR, UV/vis, XRD, SEM, and vibrating sample magnetometer (VSM) techniques. It exhibited excellent activity and selectivity in the epoxidation of olefins with oxygen in the presence of isobutyraldehyde under mild conditions (conversion 38-98%; selectivity 65-98%; and enantioselectivity 58-100%, except for alpha-methylstyrene). Furthermore, the synergistic effect of the reduced graphene oxide support was observed on the increasing activity, epoxide selectivity, and enantioselectivity. The catalyst can be recovered via magnetic separation from the reaction mixture and recycled five times without any significant loss in its activity. The advantage of this development is the use of both the synergic effect of reduced graphene oxide and the magnetite nanoparticles to obtain an easily recyclable heterogeneous green catalyst. In addition, high asymmetric induction of a rigid indanol-based unit of the ligand results in high enantioselectivity.
- Abbasi, Vahideh,Hosseini-Monfared, Hassan,Hosseini, Seyed Majid
-
p. 9866 - 9874
(2017/09/18)
-
- Asymmetric hydrolytic kinetic resolution with recyclable polymeric Co(iii)-salen complexes: A practical strategy in the preparation of (S)-metoprolol, (S)-toliprolol and (S)-alprenolol: Computational rationale for enantioselectivity
-
A series of chiral polymeric Co(iii)-salen complexes based on a number of achiral and chiral linkers were synthesized and their catalytic performances were assessed in the asymmetric hydrolytic kinetic resolution of terminal epoxides. The effects of the linker were judiciously studied and it was found that in the case of the chiral BINOL-based polymeric salen complex 1, there was an enrichment in catalyst reactivity and enantioselectivity of the unreacted epoxide, particularly in the case of short as well as long chain aliphatic epoxides. Good isolated yields of the unreacted epoxide (up to 46% compared to 50% theoretical yield) along with high enantioselectivity (up to 99%) were obtained in most cases using catalyst 1. Further studies showed that catalyst 1 could retain its catalytic activity for six cycles under the present reaction conditions without any significant loss in activity or enantioselectivity. To show the practical applicability of the above synthesized catalyst we have synthesised some potent chiral β-blockers in moderate yield and high enantioselectivity using complex 1. The DFT (M06-L/6-31+G??//ONIOM(B3LYP/6-31G?:STO-3G)) calculations revealed that the chiral BINOL linker influences the enantioselectivity achieved with Co(iii)-salen complexes. Further, the transition state calculations show that the R-BINOL linker with the (S,S)-Co(iii)-salen complex is energetically preferred over the corresponding S-BINOL linker with the (S,S)-Co(iii)-salen complex for the HKR of 1,2-epoxyhexane. The role of non-covalent C-H?π interactions and steric effects has been discussed to control the HKR reaction of 1,2-epoxyhexane.
- Roy, Tamal,Barik, Sunirmal,Kumar, Manish,Kureshy, Rukhsana I.,Ganguly, Bishwajit,Khan, Noor-Ul H.,Abdi, Sayed H. R.,Bajaj, Hari C.
-
p. 3899 - 3908
(2015/02/19)
-
- Tailoring the window sizes to control the local concentration and activity of (salen)Co catalysts in plugged nanochannels of SBA-15 materials
-
Ship shape! Chiral (salen)CoIII complexes (spheres) inside plugged nanochannels of SBA-15 materials is achieved using a ship-in-a-bottle synthesis technique. The local concentration of the metal complexes and the catalytic activity (such as the hydrolytic kinetic resolution of 1,2-epoxyalkanes; see scheme) showed a strong dependence on the size of the window. Copyright
- Shakeri, Mozaffar,Klein Gebbink, Robertus J. M.,De Jongh, Petra E.,De Jong, Krijn P.
-
p. 10854 - 10857
(2013/10/22)
-
- An efficient catalytic asymmetric epoxidation method
-
This article describes a highly effective catalytic asymmetric epoxidation method for olefins using,potassium peroxomonosulfate (Oxone, Dupont) as oxidant and a fructose-derived ketone(l) as catalyst. High enantioselectivies have been obtained-for trans-disubstituted and trisubstituted olefins which can bear functional groups such as tributylsilyl ether, acetal, chloride, and ester. The enantiomeric excesses cis-olefins and terminal olefins are not high yet. The current epoxidation shows that the catalyst efficiency is enhanced dramatically-upon raising the pH. Mechanitic studies show that the epoxidation mainly proceeds via a spiro transition state, which provides a model for predicting the stereochemical outcome of the reaction. The planar transition state, likely to be the main competing pathway. The extent of the involvement of the planar mode is subject to the steric of the alkyl groups on the olefins.
- Wang, Zhi-Xian,Tu, Yong,Frohn, Michael,Zhang, Jian-Rong,Shi, Yian
-
p. 11224 - 11235
(2007/10/03)
-
- REDUCTION OF β-HYDROXYSULFOXIDES: APPLICATION TO THE SYNTHESIS OF OPTICALLY ACTIVE EPOXIDES
-
β-hydroxysulfoxides of opposite stereochemistry can be prepared in very high diastereoisomeric excesses (90 to 95 percent) by reduction of β-ketosulfoxides with DIBAL or DIBAL/ZnCl2.A very efficient method to transform these reduction products into optically active epoxides is also described.
- Solladie, Guy,Demailly, Gilles,Greck, Christine
-
p. 435 - 438
(2007/10/02)
-
- ASYMMETRIC HALOGENATION OF CAMPHOR-10-SULFONIC ACID DERIVED ESTERS: AN EFFICIENT NEW ROUTE TO ENANTIOMERICALLY PURE HALOHYDRINS AND EPOXIDES.
-
Successive treatment of chiral esters 1 with LDA/Me3SiCl and NBS or NCS gave crystalline α-haloesters 3 which furnished halohydrins 4 and terminal epoxides 5 in high e.e..
- Oppolzer, Wolfgang,Dudfield, Philip
-
p. 5037 - 5040
(2007/10/02)
-
- Synthesis of Both the Enantiomers of 4-Dodecanolide, a Defensive Secretion of Rove Beetles
-
The enantiomers of 4-dodecanolide, a defensive secretion of rove beetles, were synthesized from (S)- and (R)-2-aminodecanoic acid obtained by the enzymic resolution of the corresponding chloroacetyl derivative.
- Sugai, Takeshi,Mori, Kenji
-
p. 2497 - 2500
(2007/10/02)
-