1489-57-2Relevant academic research and scientific papers
Chiral Supramolecular U-Shaped Catalysts Induce the Multiselective Diels-Alder Reaction of Propargyl Aldehyde
Hatano, Manabu,Sakamoto, Tatsuhiro,Mizuno, Tomokazu,Goto, Yuta,Ishihara, Kazuaki
, p. 16253 - 16263 (2018/11/27)
The Diels-Alder reaction, which is a traditional [4 + 2] cycloaddition with two carbon-carbon bond formations, is one of the most powerful tools to synthesize versatile and unique six-membered rings. We show that chiral supramolecular U-shaped boron Lewis acid catalysts promote the unprecedented multiselective Diels-Alder reaction of propargyl aldehyde with cyclic dienes. Independent from the substrate control, enantio-, endo/exo-, π-facial-, regio-, site-, and substrate-selectivities could be controlled by the present U-shaped catalysts. The obtained reaction products could access the concise synthesis of chiral diene ligands and a key intermediate of (+)-sarkomycin. The results presented here might partially contribute to the development of artificial enzyme-like supramolecular catalysts for multiselective reactions, which will be able to target organic compounds that have thus far eluded synthesis.
(Guanidine)copper Complex-Catalyzed Enantioselective Dynamic Kinetic Allylic Alkynylation under Biphasic Condition
Cui, Xi-Yang,Ge, Yicen,Tan, Siu Min,Jiang, Huan,Tan, Davin,Lu, Yunpeng,Lee, Richmond,Tan, Choon-Hong
supporting information, p. 8448 - 8455 (2018/06/22)
Highly enantioselective allylic alkynylation of racemic bromides under biphasic condition is furnished in this report. This approach employs functionalized terminal alkynes as pro-nucleophiles and provides 6- and 7-membered cyclic 1,4-enynes with high yields and excellent enantioselectivities (up to 96% ee) under mild conditions. Enantioretentive derivatizations highlight the synthetic utility of this transformation. Cold-spray ionization mass spectrometry (CSI-MS) and X-ray crystallography were used to identify some catalytic intermediates, which include guanidinium cuprate ion pairs and a copper-alkynide complex. A linear correlation between the enantiopurity of the catalyst and reaction product indicates the presence of a copper complex bearing a single guanidine ligand at the enantio-determining step. Further experimental and computational studies supported that the alkynylation of allylic bromide underwent an anti-SN2′ pathway catalyzed by nucleophilic cuprate species. Moreover, metal-assisted racemization of allylic bromide allowed the reaction to proceed in a dynamic kinetic fashion to afford the major enantiomer in high yield.
Arenophile-Mediated Dearomative Reduction
Okumura, Mikiko,Nakamata Huynh, Stephanie M.,Pospech, Jola,Sarlah, David
, p. 15910 - 15914 (2016/12/16)
A dearomative reduction of simple arenes has been developed which employs a visible-light-mediated cycloaddition of arenes with an N-N-arenophile and in situ diimide reduction. Subsequent cycloreversion or fragmentation of the arenophile moiety affords 1,3-cyclohexadienes or 1,4-diaminocyclohex-2-enes, compounds that are not synthetically accessible using existing dearomatization reactions. Importantly, this strategy also provides numerous opportunities for further derivatization as well as site-selective functionalization of polynuclear arenes.
A Versatile Route to 2-Substituted Cyclic 1,3-Dienes via a Copper(I)-Catalyzed Cross-Coupling Reaction of Dienyl Triflates with Grignard Reagents
Karlstroem, A. Sofia E.,Roenn, Magnus,Thorarensen, Atli,Baeckvall, Jan-E.
, p. 2517 - 2522 (2007/10/03)
A general synthesis of 2-substituted cyclic 1,3-dienes in two steps from α,β-unsaturated ketones has been developed. Formation of a dien-2-yl triflate followed by a copper(I)-catalyzed cross-coupling reaction with a Grignard reagent gives 2-substituted dienes in fair to excellent yields. Alkyl, aryl, and allyl Grignard reagents can be used.
Reaction of cyclic allylic acetates with aliphatic alcohols in the presence of cerium(III) chloride
Uzarewicz,Dresler
, p. 1921 - 1930 (2007/10/03)
The reactions of selected allylic acetates with methanol, ethanol, n-propyl alcohol, isopropyl alcohol and tert-butyl alcohol in the presence of catalytic amounts of cerium(III) chloride are described. Allylic alkyl ethers, bis-allylic ethers and 1,3-dienes were obtained depending on the structure of the acetates.
The reaction of cyclic allylic alcohols with aliphatic alcohols in the presence of cerium(III) chloride
Uzarewicz,Dresler
, p. 181 - 195 (2007/10/03)
Cyclic secondary and tertiary allylic alcohols react with primary aliphatic alcohols in the presence of cerium(III) chloride heptahydrate to give alkyl allylic ethers. When secondary or tertiary aliphatic alcohols are used 1,3-dienes are obtained from allylic alcohols heaving the 3-methyl-2-en-1-ol moiety (3-8, 13-15).
Isomer differentiation by tri-osmium cluster complexation of substituted 1,3-cyclohexadienes
Ingham,Johnson,Sadler,Nairn
, p. 237 - 242 (2007/10/03)
A series of methyl- and dimethyl-substituted 1,3-cyclohexadienes have been prepared from their aromatic analogues via Birch reduction and subsequent isomerisation with Fe(CO)3 fragments. These ligands were reacted with [Os3(CO)10(CH3CN)2] to form tri-osmium decacarbonyl cluster compounds containing the η4-coordinated substituted 1,3-cyclohexadienes. The various isomers of the substituted dienes show a dramatic difference in their reactivity towards the tri-osmium cluster and it is likely that this is due to the steric interactions between the methyl substituents and the cluster framework, with this effect being more marked for the di-substituted ligands.
Regioselectivity in the gas - phase nucleophilic attack on O - protonated 3-methyl-2-cyclohexen-1-ol and 1-methyl-2-cyclohexen-1-ol
Dezi, Emanuela,Lombardozzi, Antonietta,Renzi, Gabriele,Pizzabiocca, Adriano,Speranza, Maurizio
, p. 323 - 334 (2007/10/03)
Our radiolytic study of the occurrence in the gas phase of concerted SN2' reactions on several open-chain allylic oxonium ions generated in the gas phase from the attack of gaseous GA+ acids (GA+ = CnH+5 (n = 1, 2), iC3H+7, and (CH3)2F+) on suitable substrates is now continued with cyclic allylic alcohols, such as 3-methyl-2-cyclohexen-1-ol (1) and 1-methyl-2-cyclohexen-1-ol (2), with both MeOH and NMe3 as neutral nucleophiles.With MeOH as the nucleophile, the substitution reaction exclusively takes place on 1 as the starting compound, whereas when the substrate is 2 it is accompanied by extensive elimination.With NMe3, only the elimination reaction is observed in the same systems.The analysis of the isomeric distribution of the substitution and elimination products allows definition of the corresponding reaction patterns.As for open-chain oxonium ions, the nucleophilic attack on O-protonated 1 and 2 is preceded by significant intramolecular interconversion.Partial unimolecular dissociation of the same ionic intermediates also takes place.After careful evaluation of the extent of these side processes, it is demonstrated that the O-protonated 1 undergoes the concerted SN2 process with MeOH almost exclusively ( 99percent).With O-protonated 2, however, the concerted SN2' pathway (84-95percent) prevails over the classical SN2 one (6-17percent).Concomitant (E2) and elimination (E2') pathways involve attack of the selected nucleophiles on the oxonium ions from 1 and 2.Their relative extent (E2'/E2:1.78-1.96 (1); 1.43-1.70 (2)) appears only slightly dependent on the nature of the ionic substrate, the nucleophile (whether MeOH or NMe3), and the leaving group (whether H2O or MeOH).The effects of both intrinsic structural factors and experimental conditions in determining the SN2'/SN2 and E2'/E2 branchings in the selected oxonium ions is discussed and compared with related gas-phase data. - Keywords: cyclohexenols; elimination reactions; gas-phase chemistry; mechanistic studies; nucleophilic substitutions
Synthesis of Alkyl Allylic Ethers and 1,3-Dienes by the Reaction of Conjugated Cyclohexenones with Sodium Borohydride-Cerium(III) Chloride in Aliphatic Alcohols
Uzarewicz, A.,Dresler, R.
, p. 1655 - 1658 (2007/10/03)
The reaction of conjugated cyclohexenones 1,3-containing 3-methyl-2-en-1-one moiety with NaBH4/CeCl3*7H2O in primary aliphatic alcohols (MeOH, EtOH, n-PrOH) affords alkyl allylic ethers and 1,3-dienes.In isopropanol or tert-butanol only 1,3-dienes are obtained.Ketones 4-6 containing 2-methyl-2-en-1-one moiety are reduced under the same conditions to the corresponding allylic alcohols irrespective of the alcohol used.Key words: reduction, α,β-unsaturated ketones, allylic alcohols, alkyl allylic ethers, sodium borohydride, cerium(III) chloride
Thermal Decomposition of 2,3-Dihydro-1,4-benzodioxin and 1,2-Dimethoxybenzene
Schraa, Gerrit-Jan,Arends, Isabel W. C. E.,Mulder, Peter
, p. 189 - 198 (2007/10/02)
Rates and mechanisms of decomposition of 2,3-dihydro-1,4-benzodioxin (1) and 1,2-dimethoxybenzene (27) have been investigated in the gas phase near atmospheric pressure between 750 and 900 K in a tubular flow reactor in a large excess of radical trapping agents.The following rate expressions for decomposition have been determined: log kt/s-1 (1) = 15.7 - (271 kJ mol-1/2.303 RT); log kt/s-1 (27) = 15.7 - (251 kJ mol-1/2.303 RT).The main decomposition routes for 1 are the formation of o-benzoquinone (2) and 2-methyl-1,3-benzodioxole (7) through a biradical intermediate.The measured activation energy is 20 kJ mol-1 above the required C-O bond dissociation energy.Compound 2 rapidly loses CO to form cyclopenta-2,4-dien-1-one (6) which after dimerisation decomposes mainly into 3-phenylprop-2-enal (12) and indenols (14).The main product of the thermolysis of 27 is o-hydroxybenzaldehyde (33).The O-methyl bond is weakened by 16 kJ mol-1 compared to methoxybenzene as a result of the o-methoxy-substitution.
