17082-05-2Relevant articles and documents
The Electronic Interaction between the Methyl Group and Trigonal Carbon
Lambert, Joseph B.,Nienhuis, Ronald J.
, p. 6659 - 6665 (1980)
The nature of the interaction between methyl and a trigonal carbon has been examined by the effect of substituents on the methyl rotational barrier.Barriers have been measured for para-substituted toluenes and for cis- and trans-substituted propenes by the motional effects of methyl rotation on dipole-dipole spin-lattice relaxation.The toluene barriers exhibit a fair correlation with ?I and a very poor one with ?R.Thus hyperconjugation cannot be a major factor in determining the methyl rotational barrier.The propene barriers, particularly in the cis series, also correlate with ?I but have a better correlation with ?R than do the toluenes.Examination of all the 13C chemical shifts showed that the rotational barriers correlate only with the ortho carbon in the toluenes and with the 2-carbon (methyl substituted) in the propenes.These results suggest that the methyl rotational barrier is primarily sensitive to the nature of the ortho C-H bond in the toluenes and the α-C-H bond in the propenes.The ?R and ?I correlations are in accord with this model, since the ortho toluene carbon cannot interact directly through resonance with the para substituent but must depend on polar interactions.In the propenes, on the other hand, electron density at the α-carbon is determined by both inductive and resonance effects.The major factor in determining these barriers is the electron density at the critical carbon center, which is the ortho carbon for the toluenes and the α-carbon for the propenes.
Novel synthesis of α-nitroalkenes from nitroalkanes via halogenation of intermediate N,N-bis(silyloxy)enamines
Kunetsky, Roman A.,Dilman, Alexander D.,Struchkova, Marina I.,Tartakovsky, Vladimir A.,Ioffe, Sema L.
, p. 5203 - 5205 (2005)
An approach to conjugated nitroalkenes via oxidation of N,N-bis(silyloxy)enamines with bromine or iodine in the presence of tetra-n-butylammonium acetate is described. The acetate ion plays a key role by acting as a mild desilylating reagent. This new strategy allows the synthesis of α-nitroalkenes from the corresponding nitroalkanes.
CuI-Catalysed Enantioselective Alkyl 1,4-Additions to (E)-Nitroalkenes and Cyclic Enones with Phosphino-Oxazoline Ligands
Shin, Minkyeong,Gu, Minji,Lim, Sung Soo,Kim, Min-Jae,Lee, JuHyung,Jin, HyeongGyu,Jang, Yun Hee,Jung, Byunghyuck
supporting information, p. 3122 - 3130 (2018/07/06)
Catalytic enantioselective conjugate additions of simple alkyl groups to nitroalkenes or cyclic enones that result in the formation of tertiary C–C bonds are described. For these stereoselective addition reactions, new chiral phosphino-oxazoline ligands w
A greener, efficient approach to michael addition of barbituric acid to nitroalkene in aqueous diethylamine medium
Al-Najjar, Hany J.,Barakat, Assem,Al-Majid, Abdullah M.,Mabkhot, Yahia N.,Weber, Manuel,Ghabbour, Hazem A.,Fun, Hoong-Kun
, p. 1150 - 1162 (2014/02/14)
An efficient method for the synthesis of a variety of pyrimidine derivatives 3a-t by reaction of barbituric acids 1a,b as Michael donor with nitroalkenes 2a-k as Michael acceptor using an aqueous medium and diethylamine is described. This 1,4-Addition strategy offers several advantages, such as using an economic and environmentally benign reaction media, high yields, versatility, and shorter reaction times. The synthesized compounds were identified by 1H-NMR, 13C-NMR, CHN, IR, and MS. The structure of compound 3a was further confirmed by single crystal X-ray structure determination.
Metal nitrate driven nitro Hunsdiecker reaction with α,β-unsaturated carboxylic acids under solvent-free conditions
Ramgopal,Ramesh,Chakradhar,Reddy, N. Maasi,Rajanna
, p. 4043 - 4045 (2008/02/04)
Hunsdiecker reactions with α,β-unsaturated carboxylic acids were conducted under solvent-free conditions in the presence of a few drops of HNO3 together with a variety of metal nitrates [Mg(NO3)2, Sr(NO3)2], Al(NO3)3, Ca(NO3)2, Ni(NO3)2, Cd(NO3)2, Zn(NO3)2, Hg(NO3)2, AgNO3, ZrO(NO3)2, UO2(NO3)2, Th(NO3)2] or ammonium nitrate. α,β-Unsaturated aromatic carboxylic acids underwent nitro decarboxylation to afford β-nitro styrenes in moderate to good yields, while α,β-unsaturated aliphatic carboxylic acids underwent decarboxylation to yield the corresponding nitro derivatives.
N-sulfinyl metalloenamine conjugate additions: Asymmetric synthesis of piperidines
Peltier, Hillary M.,Ellman, Jonathan A.
, p. 7342 - 7345 (2007/10/03)
The first examples of conjugate additions of W-tert-butanesulfmyl metalloenamines are reported. Highly stereoselective conjugate additions (97:3 to 99:1 dr) were observed between metalloenamines derived from N-sulfinyl ketimines and α,β-unsaturated ketone
Enantioselective synthesis of α-amino acids and monosubstituted 1,2- diamines by conjugate addition of 4-phenyl-2-oxazolidinone to nitroalkenes
Lucet, Denis,Sabelle, Stephane,Kostelitz, Olivier,Le Gall, Thierry,Mioskowski, Charles
, p. 2583 - 2591 (2007/10/03)
The addition of the potassium salt of (R)- or (S)-4-phenyl-2- oxazolidinone to monosubstituted nitroalkenes proceeded with very good diastereoselectivity. Several of the addition products were converted into α-amino acids and monosubstituted 1,2-diamines of high enantiomeric purity.
Diastereo- and enantioselective synthesis of vicinal amino alcohols by oxa Michael addition of N-formylnorephedrine to nitro alkenes
Enders, Dieter,Haertwig, Andreas,Raabe, Gerhard,Runsink, Jan
, p. 1771 - 1792 (2007/10/03)
The first intermolecular asymmetric oxa Michael additions with removable chirality information within the hydroxide source are reported. As enantiopure oxygen nucleophile functioning as chiral hydroxide equivalent N-formylnorephedrine (7) was used and conjugate additions to aliphatic (E)-nitro alkenes 2a-j were carned out in good yields (35-87%) and excellent diastereomeric excesses (de = 94-≥98%). After reduction of the nitro group and protection of the amino function (11a-h, 73-87%, both steps), the cleavage of the auxiliary occurred without epimerisation (69-99%) using Na/NH3. The Boc-protected 2-amino alcohols 12a-h could be obtained in good overall yields (30-58 %, four steps) and excellent diastereomeric and enantiomeric excesses (de, ee = 94-≥98%). Transition states explaining the overall stereochemical outcome are presented based on the absolute configuration determined by X-ray structure analysis on 8b.
STEREOSPECIFICITY OF 1,3-DIPOLAR CYCLOADDITIONS OF CYCLIC NITRONES TO (E) and (Z)-β-NITROSTYRENES
Burdisso, Marina,Gamba, Anna,Gandolfi, Remo,Pevarello, Paolo
, p. 1835 - 1846 (2007/10/02)
3,4-Dihydroisoquinoline-N-oxide (1) reacted readily with (E)-β-nitrostyrene in a regiospecific reaction to give a mixture of 4-nitro-5-phenylisoxazolidines 3a and 4a resulting from endo and exo (with respect to the nitro group) transition states, respectively.This cycloaddition was found reversible under mild conditions.A careful study disclosed >= 99.89percent stereoselectivity thus narrowly circumscribing the possibility of stereochemical leakage over the cycloaddition and cycloreversion processes.Moreover, our experimental data showed that eventual loss of stereochemistry should be ascribed to base catalysed isomerizations in the adducts and/or educts.The reaction of 1 with (Z)-β-nitrostyrene (exo specific and regiospecific) turned out to be faster than that of the (E)-isomer.This is the first example of higher reactivity of a cis than a trans-alkene in 1,3-dipolar cycloadditions.The endo-trans adduct 3a cycloreverted faster than the exo-trans isomer 4a which in turn underwent fragmentation more readily than the exo-cis 6a.The cycloreversion rate was slightly enhanced by increased solvent polarity.This study was extended to the reaction of 5,5-dimethylpyrroline-N-oxide with both the cited dipolarophiles.
Cycloadditions dipolaires 1,3 aux derives nitres α ethyleniques, acetyleniques potentiels. I. Reaction avec des ylures d'azomethine. Orientation et stereochimie de la cycloaddition
Benhaoua, Hadj,Piet, Jean-Claude,Danion-Bougot, Renee,Toupet, Loic,Carrie, Robert
, p. 325 - 338 (2007/10/02)
The stereochemistry of the nitroolefins 1 prepared by known methods was unambigously established.Their reactions with azomethine ylides (e.g. 8) was studied and the stereochemistry of the adducts as well.This preliminary work was necessary to substantiate a discussion of structural (pyrrolidines conformational analysis) and mechanistic problems (dipolarophile-azomethine ylide approach and HNO2 elimination from the nitro pyrrolidines).
