- Catalytic asymmetric aldol-type reaction of zinc enolate equivalent of amides
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Treatment of phenyl isocyanate with bis(iodozincio)methane gave a zinciomethylenated product, which acts as an amide-enoate equivalent. It did not react with an aldehyde efficiently, but gave the corresponding adduct in good yield in the presence of an aminoalcohol. Use of a catalytic amount of chiral aminoalcohol led the process to the catalytic asymmetric Aldol-type reaction.
- Haraguchi, Ryosuke,Matsubara, Seijiro
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supporting information
p. 3378 - 3380
(2013/07/26)
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- Reactions of amines and hydrazides derived from L-proline with dialkyl dicyanofumarates
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The reaction of prolinamine derivatives (8a,b) and dialkyl dicyanofumarates (1) in dichloromethane at room temperature leads to the optically active enamines (10). Whereas products (10) in the case of 1-benzyl prolinamine (8a) are stable compounds, the corresponding enamines obtained from the non-protected prolinamine (8b) smoothly undergo a cyclocondensation at room temperature to give perhydropyrrolo[1,2-a]pyrazine derivatives (11). The molecular structure of 11a was established by X-Ray crystallography. In analogy to 8a, 1-benzyl prolinehydrazide (9a) and 1b in dichloromethane react to yield the enehydrazine (12b). On the other hand, the reaction of 9a and 1 in methanol at room temperature leads to the corresponding dialkyl 3-amino-1H-pyrazole- 4,5-dicarboxylates (13) and methyl 1-benzylprolinate (14b) Via a stepwise mechanism. The analogous reaction was observed between a 3-oxidoimidazole-4- carbohydrazide (15) and 1b.
- Mloston, Grzegorz,Pieczonka, Adam M.,Wroblewska, Aneta,Linden, Anthony,Heimgartner, Heinz
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p. 343 - 356
(2013/08/15)
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- Studies on the synthesis and some reactions of (S)-proline hydrazides
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A convenient synthesis of (S)-proline hydrazide 2a via the reaction of ethyl (S)-N-benzylprolinate with hydrazine hydrate and subsequent deprotection of (S)-N-benzyl proline hydrazide 5 is described. The latter, in methanolic solution, reacted with aromatic aldehydes as well as with cycloaliphatic ketones at room temperature to give the corresponding hydrazones of type 7 in good yields. The structure of the product with furan-2-carbaldehyde 7b, proving the (E)-configuration of the hydrazone, was established by X-ray crystallography. In the case of the unprotected (S)-proline hydrazide 2a, the analogous reaction with aromatic aldehydes led either to the expected hydrazones 7 or the 1H-pyrrolo[1,2-c]imidazol-1-one derivatives 8, depending on the reaction conditions. The latter were formed via a secondary cyclocondensation of the initially formed 7 with a second molecule of the aldehyde. Whereas the reaction of (S)-N-benzyl proline hydrazide 5 with butyl isocyanate and isothiocyanate gave the corresponding semicarbazide and thiosemicarbazide, respectively, of type 9, the unprotected (S)-proline hydrazide 2a yielded the 1:2 adducts 10. Thiosemicarbazide 9b underwent cyclization reactions under basic (NaOH) and acidic (H2SO4) conditions to yield (S)-prolinyl- substituted 1,2,4-triazole-3-thione 11 and 1,3,4-thiadiazole-2-amine 12, respectively.
- Mloston, Grzegorz,Pieczonka, Adam M.,Wroblewska, Aneta,Linden, Anthony,Heimgartner, Heinz
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experimental part
p. 795 - 801
(2012/09/07)
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- LARGE SCALE PREPARATION OF VERSATILE CHIRAL AUXILIARIES DERIVED FROM (S)-PROLINE
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The synthesis of a variety of enantiomerically pure chiral auxiliaries based on (S)-proline and bearing sterically demanding side chains at the pyrrolidine moiety, such as the secondary amines (S)-3,5 and 7 and the hydrazines (S)-6, is described on a molar scale.As key step, the Grignard or RLi addition to the N-benzylated proline ester (S)-1 is used.
- Enders, Dieter,Kipphardt, Helmut,Gerdes, Peter,Brena-Valle, Leonardo J.,Bhushan, Vidya
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p. 691 - 704
(2007/10/02)
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