2-Oxazolidinone pyrrolidine derivative from

Many chiral auxiliaries are derived from 1,2-amino alcohols [7], including oxazolidinones (1) [7-9], oxazolines (2) [10,11], bis-oxazolines (3) [12,13], oxa-zinones (4) [14], and oxazaborolidines (5) [15-17]. Even the 1,2-amino alcohol itself can be used as a chiral auxiliary [18-22]. Other chiral auxiliary examples include camphorsultams (6) [23], piperazinediones (7) [24], (S)-l-amino-2-(methoxymethyl)-pyrrolidine (SAMP) (8) and (R)-l-amino-2-(methoxymethyl)-pyrrolidine (RAMP) [25], chiral boranes such as isopinocampheylborane (9) [26], and tartaric acid esters (10). Some of these auxiliaries have been used as ligands... 

McQuade and co-workers [41] found that while the rate of proline-catalyzed a-aminoxylation of aldehydes in chloroform or ethyl acetate is significantly increased by the presence of a bifunctional urea, this effect is not observed when the catalyst is a 2-pyrrolidine-tetrazole, which cannot form an oxazolidinone. On the other hand, a similar rate acceleration was observed when the catalyst was the preformed Seebach oxazolidinone derived from proline and hexanal, or the soluble trans-A- tert- saiy di-methylsilyloxy)proline. NMR studies also showed that the role of the urea was to promote both (a) pro line solubilization by formation of the oxazolidinone (not by direct... 

A nucleophilic attack of methanol in the a-position to a nitrogen atom can take place through an electrochem-ically generated iminium cation from substituted pyrrolidine [171,172], piperidine [173-180] or oxazolidinone [181,182] derivatives, as illustrated in Scheme 99 for A-carbomethoxypyrrolidine [163] and N-carbomethoxypiperidine [174]. 

Extension of the enamine-mediated carbonyl a-amination strategy to the generation of quaternary stereogenic centers at the a-position of a-branched aldehydes under catalysis by prohne 1 [8, 9], pyrrolidine tetrazole 3 [10, 11], or L-azetidin-2-carboxylic acid 4 [8] has also been explored (Table 11.1). The observed enantio-selectivities ranged from essentially none to >99%. Derivatives of 2-phenylpropanal gave better enantioselectivities than a,a-dialkyl substituted aldehydes. Erase and coworkers [11] employed microwave irradiation to accelerate the rate of proline-catalyzed amination, and found that yields as well as enantioselectivity can be somewhat improved with shorter reaction times. It appears that the pyrrolidine tetrazol 3 was a more effective catalyst than L-proline 1 for the amination of 2-phenylpropanal derivatives [10,11]. Subsequent reduction of adducts and cyclization could be carried out to afford the respective a-amino alcohols or the A-amino-oxazolidinones. 

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