7386-65-4Relevant articles and documents
Contra-thermodynamic E → Z isomerization of cinnamamides via selective energy transfer catalysis
Becker, Marc R.,Morack, Tobias,Robertson, Jack,Metternich, Jan B.,Mück-Lichtenfeld, Christian,Daniliuc, Constantin,Burley, Glenn A.,Gilmour, Ryan
supporting information, (2020/05/25)
A bio-inspired, photocatalytic E → Z isomerization of cinnamides is reported using inexpensive (?)-riboflavin (vitamin B2) under irradiation at λ = 402 nm. This operationally simple transformation is compatible with a range of amide derivatives including –NR2, –NHSO2R and N(Boc)2 (up to 99:1 Z:E). Selective energy transfer from the excited state photocatalyst to the starting E-isomer ensures that directionality is achieved: The analogous process with the Z-isomer is inefficient due to developing allylic strain causing chromophore deconjugation. This is supported by X-ray analysis and Stern-Volmer photo-quenching studies. Preliminary validation of the method in manipulating the conformation of a simple model Leu-enkephalin penta-peptide is disclosed via the incorporation of a cinnamamide-based amino acid.
Chiral 1,3,2-Diazaphospholenes as Catalytic Molecular Hydrides for Enantioselective Conjugate Reductions
Miaskiewicz, Solène,Reed, John H.,Donets, Pavel A.,Oliveira, Caio C.,Cramer, Nicolai
, p. 4039 - 4042 (2018/03/13)
Secondary 1,3,2-diazaphospholenes have a polarized P?H bond and are emerging as molecular hydrides. Herein, a class of chiral, conformationally restricted methoxy-1,3,2-diazaphospholene catalysts is reported. We demonstrate their catalytic potential in asymmetric 1,4-reductions of α,β-unsaturated carbonyl derivatives, including enones, acyl pyrroles, and amides, which proceeded in enantioselectivities of up to 95.5:4.5 e.r.
Photocatalytic E → Z isomerization of polarized alkenes inspired by the visual cycle: Mechanistic dichotomy and origin of selectivity
Metternich, Jan B.,Artiukhin, Denis G.,Holland, Mareike C.,Von Bremen-Kuhne, Maximilian,Neugebauer, Johannes,Gilmour, Ryan
, p. 9955 - 9977 (2018/05/31)
Iteratively executed with exquisite spatial and temporal control, the selective isomerization of polarized alkenes underpins a plethora of complex biological processes ranging from natural product biosynthesis through to the mammalian visual cycle. However, nature's proficiency conceals the inherent difficulties in replicating this contrathermodynamic transformation in the laboratory. Recently, we disclosed the first highly Z-selective isomerization of polarized alkenes, employing the cinnamoyl chromophore as a retinal surrogate under UV-irradiation (402 nm) with (-)-riboflavin (Vitamin B2) as an inexpensive, organic photocatalyst (J. Am. Chem. Soc. 2015, 137, 11254-11257). This study was inspired by the propensity of crystalline (-)-riboflavin in the eyes of vertebrates to invert the intrinsic directionality of retinal isomerization. Herein, we extend this methodology to include a bioinspired, catalytic E → Z isomerization of α,β-unsaturated nitriles, thereby mimicking the intermediate Opsin-derived, protonated Schiff base in the visual cycle with simple polarized alkenes. Replacement of the iminium motif by a cyano group is well tolerated and gives an additional degree of versatility for postisomerization functionalization. Broad substrate scope is demonstrated (up to 99:1 Z:E) together with evidence of mechanistic dichotomy via both singlet and triplet energy transfer mechanisms. Kinetic studies, temperature dependent photostationary state correlations and investigation of substituent-based electronic perturbation of the alkene identified polarization combined with increased Z-isomer activation barriers as the selectivity governing factors in catalysis. This investigation demonstrates the importance of internal structural preorganization on photostationary composition and explicates the augmented Z-selectivity upon hydrogen-alkyl exchange at the β-position of the alkene.
Rhodium-Catalyzed Asymmetric Hydrogenation of α,β-Unsaturated Carbonyl Compounds via Thiourea Hydrogen Bonding
Wen, Jialin,Jiang, Jun,Zhang, Xumu
, p. 4451 - 4453 (2016/09/28)
The strategy of secondary interaction enables enantioselectivity for homogeneous hydrogenation. By introducing hydrogen bonding of substrates with thiourea from the ligand, α,β-unsaturated carbonyl compounds, such as amides and esters, are hydrogenated wi
Radical cyclizations of conjugated esters and amides with 3-oxopropanenitriles mediated by manganese(III) acetate
Yilmaz, E. Vildan Burgaz,Yilmaz, Mehmet,Oektemer, Atilla
, p. 363 - 376 (2011/09/20)
Radical cyclizations of conjugated esters and amides with 3-oxopropanenitriles in presence of manganese(III) acetate produced ethyl 4-cyano-2,3-dihydrofuran-3-carboxylates and 4-cyano-2,3-dihydrofuran-3- carboxamides in good yields. The radical cyclizations of conjugated amides gave 2,3-dihydrofurans in better yields than that of conjugated esters. Moreover, the reactions of thienyl substituted amides and esters with 3-oxopropanenitriles afforded 2,3-dihydrofurans more efficiently than phenyl substituted ones. ARKAT-USA, Inc.
The HWE reaction in solid - liquid two phase system for the synthesis of α,β-unsaturated amides
Petrova, Jordanka,Momchilova, Snezhana,Vassilev, Nikolay G.
, p. 87 - 94 (2007/10/03)
The Horner-Wadsworth-Emmons (HWE) reaction of the diethyl ester of 2-amino-2-oxoethylphosphonic acid 1 as well as of diethyl ester of the 2-dimethylamino-2-oxoethylphosphonic acid 2 with some aldehydes and ketones 3 in liquid-solid two phase system is used for the preparation of α,β-unsaturated amides 4, 5. The synthesis is carried out in mild conditions (room temperature, KOH, K2CO3, CaO) in the absence of a catalyst or in the absence of a solvent, and leads in very high (E)-stereoselectivity and in high yields to en-amides.
