New learning discoveries about 147959-19-1

With the rapid development and complex challenges of chemical substances, new drug synthesis pathways are usually the most effective.147959-19-1,(S)-tert-Butyl 2,2-dimethyl-4-(2-oxoethyl)oxazolidine-3-carboxylate,as a common compound, the synthetic route is as follows.

With key building block 6 in hand, its nitroaldol (Henry) reaction with nitromethane was examined (Table 1). LiAlH418- TBAF19- as well as t-BuOK20-catalyzed Henry reactions led to nitro alcohols 12 and 13 with low diastereoselectivity, reflecting that the existing stereogenic center is too far away from the newly created one to exert appreciable asymmetric induction (Table 1, entries 1-3).21 An obvious way of resolving this problem was the introduction of additional chiral information, i.e. application of a chiral catalyst. In fact double stereodifferentiation using Shibasaki’s well established heterobimetallic (,S)-BINOL catalyst 1422 (5 mol%, THF, -40 C, 3 d) led to 12 with high diastereoselectivity albeit in low yield (Table 1, entry 4).Recently, other highly efficient chiral catalysts for asymmetric Henry reactions have been developed. Thus, Corey23 and Maruoka24 have utilized chiral quaternary ammonium fluorides as catalysts while Trost25 has presented a dinuclear zinc catalyst. Salen-cobalt(II) complexes have been used by Yamada whereas J¡ãrgensen and Evans have introduced bis(oxazoline)-coprhoer(II) complexes. The latter seemed to be the catalysts of choice, at least for aliphatic aldehydes, with respect to attainable yields and degree of stereoselectivity. EPO Table 1. Diastereoselective Henry Reaction of Aldehyde 6 with Nitromethaneyield ratio0 entry catalyst conditions(%)a 12:131 LiAlH4 THF, rt 53 56:442 TBAF THF, rt 33 43:573 r-BuOK t- 72 23:77BuOH/THF,00C4 14 THF, -40 C 45 98:25 {Cu[(+> EtOH, rt 87 92:815]} (OAc)26 (CuK-)- EtOH, rt 85 9:9115]}(OAc)27 {Cu[(+> EtOH, rt 94 97:316]}(OAc)28 (Cu[(-)- EtOH, rt 91 8:9216I)(OAc)2a isolated yield b determined by HPLC analysis of crude reaction mixtures EPO Indeed application of Evans’ bis(oxazoline) copper(II) acetate-based catalysts {Cu[(+)- 15]}(OAc)2 and in particular {Cu[(+)-16]}(OAc)2 (5 mol%, EtOH, rt, 5 d) gave the desired nitro alcohol 12 both with high diastereoselectivity and in high yield (Table 1 , entries 5 and 7). Finally, to obtain selectively diastereomer 13, aldehyde 6 was reacted with nitromethane in the presence of the enantiomeric catalysts {Cu[(-)-15]}(OAc)2 and {Cu[(-)-16]} (OAc)2 respectively. In these cases slightly lower stereoselectivities and yields were observed reflecting a mismatched pairing (Table 1, entries 6 and 8).

As the paragraph descriping shows that 147959-19-1 is playing an increasingly important role.

Reference£º
Patent; LUDWIG-MAXIMILIANS-UNIVERSITAET MUENCHEN; WO2006/94770; (2006); A2;,
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