- Aza-Darzens asymmetric synthesis of N-(p-toluenesulfinyl)aziridine 2- carboxylate esters from sulfinimines (N-sulfinyl imines)
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The one-step aza-Darzens reaction of sulfinimines 2 with lithium α- bromoenolates readily affords diversely substituted cis and trans N- sulfinylaziridine 2-carboxylate esters 3 and 7 in good yield and excellent diastereoselectivity. Higher yields, but lower de's, result when a mixture of the α-bromo ester and 2 are treated with base. The N-sulfinyl group is transformed, nearly quantitatively, without ring opening, into the N-tosyl activating group by oxidation with m-CPBA. Selective removal of the N- sulfinyl group in aziridines 3a and 3h with TFA/H2O affords 1H-aziridines 21 which are difficult to prepared by other means. However, C(3) activated azirines such as 3b undergo ring-opening under these conditions. Alternatively, the N-sulfinyl group, even in C(3)-activated aziridines, was selectively and efficiently removed by treatment of the aziridine with 2 equiv of MeMgBr.
- Davis, Franklin A.,Liu, Hu,Zhou, Ping,Fang, Tianan,Reddy, G. Venkat,Zhang, Yulian
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p. 7559 - 7567
(2007/10/03)
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- Transition metal-catalyzed regioselective and stereoselective aminochlorination of cinnamic esters
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(formula presented) A new aminohalogenation process has been developed for the synthesis of vicinal haloamine derivatives using cinnamic esters as substrates. The reaction was performed in CH3CN using ZnCl2 or Cu(OTf)2 as catalyst and N,N-dichloro-p-toluenesulfonamide as chlorine/nitrogen source. Good to excellent yields and regio-and stereoselectivities have been obtained. The stereochemistry was unambiguously determined by transforming one of the products to a known sample.
- Li, Guigen,Wei, Han-Xun,Kim, Sun Hee,Neighbors, Margret
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p. 395 - 397
(2008/02/11)
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- Aziridine compounds, methods of preparation and reactions thereof
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Novel N-sulfinyl-2-carboxyaziridine compounds and novel N-hydrogen-2-hydroxymethylaziridine compounds are provided. The asymmetric synthesis of N-sulfinylaziridines is readily accomplished in high diastereomeric purity and good yield by the Darzens-type reaction of the metal enolate of an α-haloester and an enantiopure sulfinimine. Ring-opening of these aziridines affords α-amino acids and the otherwise difficult to prepare syn-β-hydroxy-α-amino acids, both key structural units found in many bioactive materials. The N-sulfinyl radical may be selectively removed from the novel aziridine compounds by treatment with acid or base. Alternatively, the N-sulfinyl radical may be oxidized to provide the corresponding N-sulfonyl-aziridine, or reduced to form the corresponding 1H-2-hydroxymethylaziridine, either of which may subsequently be ring-opened to provide precursors to bioactive compounds.
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- Asymmetric Synthesis and Reactions of cis-N-(p-Toluenesulfinyl)aziridine-2-carboxylic Acids
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cis-Aziridine-2-carboxylic acids, 2, precursors of the difficult to prepare syn-β-hydroxy-α-amino acid structural unit, are prepared in high diastereomeric purity by a Darzens-type reaction of the lithium enolate of methyl bromoacetate with enantiopure sulfinimines 1.
- Davis, Franklin A.,Zhou, Ping,Reddy, G. Venkat
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p. 3243 - 3245
(2007/10/02)
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