60096-50-6Relevant academic research and scientific papers
Diastereo- and enantioselective synthesis of 2,3- and 1,2-disubstituted 4-oxophosphonates via asymmetric Michael addition
Enders, Dieter,Wahl, Heiner,Papadopoulos, Kyriakos
, p. 12961 - 12978 (1997)
Asymmetric Michael addition of lithiated SAMP hydrazones (S)-2 to a variety of alkenylphosphonates (E)-3 followed by oxidative cleavage of the 1,4-adducts 4 afforded 2,3-disubstituted 4-oxophosphonates 5 with good to very good yields (58-80%), low to moderate diastereomeric (de = 6-74%) and excellent enantiomeric excesses (ee = >93%). Pure anti-diastereomers (ee = >93%) of 5 were obtained by separation of the stereoisomers by HPLC. In addition, the lithiated SAMP hydrazone (S)-2a was added to alkenylphosphonates (E)-3, and the lithio phosphonate anions were trapped with alkyl halides or sulfates, yielding 1,2-disubstituted 4-oxophosphonates 8 with moderate to good yields (38-69%), low to good diastereomeric (de = 10-77%) and high enantiomeric excesses (ee = >90%) after oxidative cleavage.
ENANTIOSELECTIVE SYNTHESIS OF PROTECTED α-HYDROXY ALDEHYDES AND KETONES VIA HYDROXYLATION OF METALATED CHIRAL HYDRAZONES
Enders, Dieter,Bhushan, Vidya
, p. 2437 - 2440 (2007/10/02)
α-Benzyloxy aldehydes and α-acetoxy ketones 4 of high enantiomeric purity are prepared in good overall yields via oxaziridine mediated hydroxylation of chiral hydrazone azaenolates.As auxiliaries novel proline derived hydrazine reagents 5 are used.
Asymmetric Michael Additions via SAMP-/RAMP-Hydrazones Enantioselective 1,4-Addition of Methyl Ketones to Knoevenagel Acceptors
Enders, Dieter,Demir, Ayhan S.,Rendenbach, Beatrice E. M.
, p. 1731 - 1736 (2007/10/02)
Asymmetric Michael addition of lithiated methyl ketone SAMP-hydrazones (S)-2 to 2-benzylidenemalonates and -dinitriles 3 followed by oxidative cleavage of the 1,4-adducts (SR)-4 by ozonolysis affords 2-substituted 4-oxo diesters and -dinitriles (R)-5 in good overall yields of 50-82percent and high enantiomeric excesses (ee >/= 95percent).
ASYMMETRIC MICHAEL ADDITIONS VIA SAMP-/RAMP-HYDRAZONES ANTI-DIASTEREO- AND ENANTIOSELECTIVE SYNTHESIS OF 3,4-DISUBSTITUTED 5-OXO-ALKANOATES
Enders, Dieter,Papadopoulos, Kyriakos,Rendenbach, Beatrice E.M.,Appel, Rolf,Knoch, Falk
, p. 3491 - 3494 (2007/10/02)
An efficient and highly anti-diastereo-(de=90-100percent) and enantioselective (ee=92-100percent) synthesis of 3,4-disubstituted 5-oxo-alkanoates 3 in good overall chemical yields is described.The procedure involves the asymmetric Michael addition of aldehydes or ketones to enoates via their lithiated SAMP-/RAMP-hydrazones.Both enantiomers are accessible at will.
ASYMMETRIC MICHAEL ADDITIONS VIA SAMP-/RAMP-HYDRAZONES ENANTIOSELECTIVE SYNTHESIS OF PHEROMONES OF THE SMALL FOREST ANT (FORMICA POLYCTENA) AND THE RED WOOD ANT (F. RUFA)
Enders, Dieter,Rendenbach, Beatrice E. M.
, p. 2235 - 2242 (2007/10/02)
A simple and efficient asymmetric synthesis of the pheromones of the small forest ant (Formica polyctena) and the red wood ant (F. rufa) is described.The key step is an asymmetric Michael addition of lithiated propanal-SAMP- or RAMP-hydrazone to enoates with virtually complete asymmetric induction (de,ee 96percent).
ASYMMETRIC SYNTHESES VIA METALATED CHIRAL HYDRAZONESOVERALL ENANTIOSELECTIVE α-ALKYLATION OF ACYCLIC KETONES
Enders, D.,Eichenauer, H.,Baus, U.,Schubert, H.,Kremer, K. A. M.
, p. 1345 - 1359 (2007/10/02)
A general method is described, which allows the overall enantioselective α-alkylation of acyclic ketones in good overall yields (44-86percent, 4 steps) and enantioselectivities ranging routinely from >94percent ee up to virtually complete asymmetric induction (99.5percent ee).The acyclic ketones are transformed to their corresponding "SAMP-hydrazones" (S)-2 by reaction with the enantiomerically pure hydrazine (S)-1-amino-2-methoxymethyl-pyrrolidine , readily available from (S)-proline.Metalation to form chiral azaenolates (S)-3 of ECCZCN-configuration and then alkylation to product hydrazones 4, followed by hydrazone cleavage via acidic hydrolysis of methiodides 9 in a two phase system or ozonolysis, leads to α-substituted, enantiomerically enriched, acyclic ketones 5.In special cases, where a phenyl group is directly attached to the newly generated center of chirality (5n,o,p), only low enantiomeric excesses are observed. 17 Examples, including first applications in natural product synthesis (cf 5a,b,e, and h) are summarized.
ASYMMETRIC SYNTHESIS OF β-SUBSTITUTED δ-KETOESTERS VIA MICHAEL-ADDITIONS OF SAMP/RAMP-HYDRAZONES TO α,β-UNSATURATED ESTERS, VIRTUALLY COMPLETE 1.6-ASYMMETRIC INDUCTION
Enders, Dieter,Papadopoulos, Kyriakos
, p. 4967 - 4970 (2007/10/02)
A simple and efficient 3-step asymmetric synthesis of β-substituted δ-ketoesters 3 in 45-62percent overall chemical yield and >=96-ca.100percent ee is described.The key step is an asymmetric Michael-addition of lithiated methylketone-SAMP- or RAMP-hydrazones to α,β-unsaturated esters 2 with virtually complete 1.6-asymmetric induction.
