299216-13-0Relevant articles and documents
A simple and efficient approach to the N-amination of oxazolidinones using monochloroamine
Huynh, Uyen,Uddin, Md. Nasir,Wengryniuk, Sarah E.,McDonald, Stacey L.,Coltart, Don M.
, p. 4799 - 4802 (2016)
Chiral nonracemic N-amino cyclic carbamates (ACCs) are important auxiliaries for certain asymmetric transformations. In the past they have been synthesized from oxazolidinones using methods that require the preparation and use of non-atom economical aminating agents that can be difficult to prepare, and often strong bases. In what follows we describe a mild and operationally simple method for the direct N-amination of oxazolidinones that use NH2Cl derived from commercial bleach.
On the regioselectivity and diastereoselectivity of ACC hydrazone alkylation
Huynh, Uyen,Uddin, Md. Nasir,Wengryniuk, Sarah E.,McDonald, Stacey L.,Coltart, Don M.
supporting information, p. 432 - 436 (2017/01/13)
The asymmetric α-allylation of 3-pentanone using several different N-amino cyclic carbamate (ACC) auxiliaries is described. The level of asymmetric induction was found to range from er?=?93:7 to er?=?99:1. The factors that lead to compromised selectivity
A novel hydrazide type organocatalyst for enantioselective Diels-Alder reactions
Suzuki, Ichiro,Ando, Masafumi,Shimabara, Rumiko,Hirata, Ai,Takeda, Kei
supporting information; experimental part, p. 3033 - 3040 (2011/05/30)
The development of a new class of hydrazide type organocatalyst, (4R,5R)-1,3-bis(isopropylamino)-4,5-dihenylimidazolidin-2-one 2a, for enantioselective Diels-Alder reactions between cyclopentadiene and α,β-unsaturated aldehydes are presented. The new organocatalyst 2a promoted the reaction, affording Diels-Alder adducts in good yields with good levels of enantioselectivity.
Regioselective asymmetric α,α-bisalkylation of ketones via complex-induced Syn -deprotonation of chiral N -amino cyclic carbamate hydrazones
Wengryniuk, Sarah E.,Lim, Daniel,Coltart, Don M.
supporting information; experimental part, p. 8714 - 8720 (2011/07/30)
The first general method for the asymmetric α,α-bisalkylation of ketones having both α- and α′-protons is described. Both excellent regio- and stereoselectivity result. The transformation is enabled by complex-induced syn-deprotonation (CIS-D), which completely reverses the inherent preference of lithium diisopropylamide (LDA) to remove the less sterically hindered of two similarly acidic protons. CIS-D also overrides the normal tendency of LDA to remove the more strongly acidic proton in a substrate having protons differing significantly in their acidity. The regiochemical outcome is, thus, the opposite of that normally obtained for kinetic LDA-mediated deprotonation of ketones and (S)-1-amino-2- methoxymethylpyrrolidine/(R)-1-amino-2-methoxymethylpyrrolidine (SAMP/RAMP)hydrazones. Conveniently, this strategy allows access to either ketone enantiomer using a single enantiomer of the auxiliary. The utility of this method is demonstrated by a concise and highly efficient formal synthesis of both (R)- and (S)-stigmolone.
Mn-mediated coupling of alkyl iodides and ketimines: A radical addition route to α,α-disubstituted α-aminoesters
Friestad, Gregory K.,Ji, An
scheme or table, p. 2311 - 2313 (2009/05/11)
(Chemical Equation Presented) Coupling of primary and secondary alkyl iodides with N-acylhydrazonoesters via Mn-mediated photolysis conditions affords access to tert-alkyl amines.
Simple and efficient asymmetric α-alkylation and α,α- bisalkylation of acyclic ketones by using chiral N-amino cyclic carbamate hydrazones
Lim, Daniel,Coltart, Don M.
experimental part, p. 5207 - 5210 (2009/04/11)
(Chemical Equation Presented) Distinguishing left from right: In the title reactions, chiral N-amino cyclic carbamates (ACCs) substantially diminish the drawbacks associated with the use of chiral dialkyl hydrazines, yet provide excellent stereoselectivity and high yields. In addition, ACCs exhibit a unique directing effect that overrides the inherent selectivity of lithium diisopropylamide (LDA) and enables the asymmetric α,α-bisalkylation of ketones (see scheme).
Radical addition approach to asymmetric amine synthesis: Design, implementation, and comparison of chiral N-acylhydrazones
Friestad, Gregory K.,Draghici, Cristian,Soukri, Mustapha,Qin, Jun
, p. 6330 - 6338 (2007/10/03)
Intermolecular radical addition to C=N bonds with acyclic stereocontrol offers excellent potential as a mild, nonbasic carbon-carbon bond construction approach to chiral amines. Here, complete details of the first radical additions to chiral N-acylhydrazones as an approach to asymmetric amine synthesis are disclosed. Novel N-acylhydrazones were designed as chiral C=N radical acceptors with Lewis acid activation, restriction of conformational mobility, and commercial availability of precursors. Amination of 4-alkyl-2-oxazolidinones with O-(mesitylenesulfonyl)hydroxylamine or O-(p-nitrobenzoyl)hydroxylamine afforded N-aminooxazolidinones which were condensed with aldehydes to afford N-acylhydrazones 3-8. Three synthetic methods were developed, implementing these N-acylhydrazones in Lewis acid-promoted intermolecular radical additions to C=N bonds. First, additions of various secondary and tertiary alkyl iodides to propionaldehyde and benzaldehyde hydrazones (3 and 7) under tin hydride radical chain conditions in the presence of ZnCl2 gave N-acylhydrazine adducts with diastereomeric ratios ranging from 93:7 to 99:1. Radical additions to a series of N-acylhydrazones with different substituents on the oxazolidinone revealed that benzyl and diphenylmethyl were more effective stereocontrol elements than those with the aromatic ring directly attached to the oxazolidinone. Second, a tin-free method, exploiting dual functions of triethylborane for both initiation and chain propagation, enabled improved yields in addition of secondary alkyl iodides. Third, under photolytic conditions with hexamethylditin, primary radical addition could be achieved with ethyl iodide in the presence of diethyl ether as cosolvent; the 1-ethoxyethyl adduct was observed as a minor product. Chloromethyl addition was achieved under both the tin-free and photolytic conditions; in this case, the adduct bears alkyl chloride functionality with potential for further elaboration.
Highly diastereoselective indium-mediated allylation of chiral hydrazones
Cook, Gregory R.,Maity, Bikash C.,Kargbo, Robert
, p. 1741 - 1743 (2007/10/03)
Matrix presented. The indium-mediated allylation of chiral hydrazones was investigated. Essentially complete diastereoselectivity and quantitative yields were obtained for substrates derived from both aromatic and aliphatic aldehydes.
Diastereoselective intermolecular addition of the 1,3-dioxolanyl radical to N-acyl aldohydrazones. Asymmetric synthesis of α-amino acid derivatives
Fernandez, Marta,Alonso, Ricardo
, p. 2461 - 2464 (2007/10/03)
(Matrix presented) N-Acyl aldohydrazones I (R = CO2Et, alkyl, aryl, and furyl) efficiently trap the 1,3-dioxolanyl radical intermolecularly without external activation at temperatures as low as -78°C. For alkyl aldohydrazones, good diastereoselectivities are obtained in the presence of InCl3 at low temperature. Elaboration of the adducts (II) allows for the asymmetric synthesis of α-amino acid derivatives.
Comparison of electrophilic amination reagents for N-amination of 2-oxazolidinones and application to synthesis of chiral hydrazones.
Shen, Yuehai,Friestad, Gregory K
, p. 6236 - 6239 (2007/10/03)
Comparison of several hydroxylamine-based electrophilic ammonia equivalents in the N-amination of 2-oxazolidinones revealed that O-(p-nitrobenzoyl)hydroxylamine (NbzONH(2)) and sodium hydride in dioxane is a superior reagent combination for this purpose. Practical preparations of a variety of chiral N-acylhydrazones by this method gave yields ranging from 45 to 95%. Methods for exchange or removal of the aldehyde component have been developed, making this a general route to chiral N-acylhydrazones of interest for asymmetric synthesis applications.
