80698-12-0Relevant articles and documents
4-ferrocenyl-1,3-oxazoline derivatives as ligands for catalytic asymmetric allylation reactions
Moreno, Rosa Ma,Bueno, Agustí,Moyano, Albert
, p. 62 - 70 (2002)
Bis(oxazolines) and 2-(2-phosphinoaryl)oxazolines derived from highly enantiopure 2-amino-2-ferrocenylethanol have been tested as ligands in the asymmetric Pd(0)-catalysed allylic alkylation reaction. Essentially complete enantioselectivity (99.8:0.2 er) has been achieved in the nucleophilic substitution of 1,3-diphenyl-2-propenyl acetate by dimethyl malonate anion. The absolute configuration of the ligands has been unambiguously established by chiroptical methods.
Transesterification of N-acyloxazolidinones with alcohol by lanthanum(III) iodide
Fukuzawa, Shin-Ichi,Hongo, Yuki
, p. 3521 - 3524 (2007/10/03)
Transesterification of N-acyloxazolidinones by treatment with an alcohol and lanthanum(III) iodide gives the corresponding esters in good to excellent yields under mild conditions with negligible racemization.
A useful modification of the Evans auxiliary: 4-Isopropyl-5,5- diphenyloxazolidin-2-one
Hintermann, Tobias,Seebach, Dieter
, p. 2093 - 2126 (2007/10/03)
The 4-isopropyl-5,5-diphenyloxazolidinone (1) is readily prepared from (R)- or (S)-valine ester, PhMgBr, and ethyl chlorocarbonate. It has a melting point of ca. 250°, a low solubility in most organic solvents, and a C=O group which is sterically protected from nucleophilic attack. Thus, the soluble N-acyl-oxazolidinones (7-16) can be prepared from 1 with BuLi at temperatures around 0°instead of - 78°(Scheme 3), their Li enolates can be generated with BuLi, rather than with LDA, and deacylation in the final step of the procedure can be achieved with NaOH at ambient temperatures (Scheme 12), with facile recovery of the precipitating auxiliary 1 (filtering, washing, and drying). The following reactions of N-acyl-oxazolidinones from 1 have been investigated: alkylations (Scheme 4), aminomethylations and hydroxymethylations (Scheme 5), aldol additions (Schemes 6 and 7), Michael additions (Schemes 9 and 10), and a (4 + 2) cycloaddition (Scheme 11). The well-known features of reactions following the Evans methodology (yield, diastereoselectivity, dependence on conditions, counter ions, additives etc.) prevail in these transformations. Most products, however, have higher melting points and a much more pronounced crystallization tendency than those derived from conventional oxazolidinones, and can thus be purified by recrystallization, avoiding chromatography (Table 1). The disadvantage of 1 having a higher molecular weight (ca. 150 Da) than the non-phenyl-substituted auxiliary is more than compensated by the ease of its application, especially on large scale. A number of crystal structures of oxazolidinones derived from 1 and a TiCl4 complex of an oxazolidinone are described and discussed in view of the diastereoselective-reaction mechanisms.
4-Substituted-5,5-Dimethyl Oxazolidin-2-ones as Effective Chiral Auxiliaries for Enolate Alkylations and Michael Additions
Davies, Stephen G.,Sanganee, Hitesh J.
, p. 671 - 674 (2007/10/02)
4-(Methyl, phenyl, benzyl, and i-propyl)-5,5-dimethyl-oxazolidin-2-ones, readily available from α-amino acids, are shown to be effective chiral auxiliaries for stereoselective enolate alkylations and conjugate additions of attached N-acyl moieties.
Asymmetric aldol and alkylation reactions mediated by the 'quat' chiral auxiliary (R)-(-)-5-methyl-3,3-dimethyl-2-pyrrolidinone
Davies,Doisneau,Prodger,Sanganee
, p. 2373 - 2376 (2007/10/02)
Enolates derived from the N-propionoyl derivative of the 'quat' chiral auxiliary (R)-(-)-5-methyl-3,3-dimethyl-2-pyrrolidinone undergo highly stereoselective aldol and alkylation reactions. Removal of the auxiliary has been demonstrated with LiOH, PhCH2OLi, MeOMgBr and LiAlH4 to generate respectively (2R,3R)-3-hydroxy-2-methyl-3-phenylpropionic acid in homochiral form, and with 96% e.e. (S)-2-methyl-3-phenylpropionic acid and derived methyl and benzyl esters and with >94% e.e. (S)-2-methyl-3-phenylpropanol.
Asymmetric alkylation reactions of camphor-based imide enolate
Yan,Chu,Lin,Wu,Liu
, p. 4959 - 4962 (2007/10/02)
Alkylations of lithium-chelated imide enolate derived from camphor-based oxazolidone with a variety of alkyl halides provide alkylated products with good to excellent diastereoselectivity.
