- An improved procedure for the asymmetric aldol reaction of the titanium enolate of an N3-propionyl-3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one
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The direct formation of the titanium enolate of N3-propionyl-3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one has been achieved through complexation with titanium tetrachloride at 25°C, followed by deprotonation with triethylamine (-78 to 25°C). The preformed titanium enolate has been reacted with D2O/DCl to afford deuterated derivative 6 and also reacted with a series of aromatic and aliphatic aldehydes affording aldol adducts 4a-f with crude diastereoselectivities ranging from 8:1 to 38:1.
- Casper, David M.,Hitchcock, Shawn R.
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- Formation of Complex Hydrazine Derivatives via Aza-Lossen Rearrangement
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The development of a broadly applicable procedure for the aza-Lossen rearrangement is reported. This process converts amines into complex hydrazine derivatives in two steps under safe, mild conditions. This method allows the chemoselective formation of N-
- Polat, Dilan E.,Brzezinski, David D.,Beauchemin, André M.
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supporting information
p. 4849 - 4852
(2019/06/27)
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- Towards the development of oxadiazinanones as chiral auxiliaries: synthesis and application of N3-haloacetyloxadiazinanones
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Oxadiazinanones derived from (1R,2S)-ephedrine and (1R,2S)-norephedrine were employed in the asymmetric α-halo aldol reaction. The optimized yields and diastereoselectivities for the ephedrine based oxadiazinanone aldol reaction ranged from fair to good.
- Hoover, Trisha R.,Groeper, Jonathan A.,Parrott II, Raleigh W.,Chandrashekar, Seshanand P.,Finefield, Jennifer M.,Dominguez, Alexandro,Hitchcock, Shawn R.
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p. 1831 - 1841
(2007/10/03)
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- Synthesis, X-ray crystallography and computational studies concerning an oxadiazinone derived from D-camphor: A structural limitation of oxadiazinones as chiral auxiliaries
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A camphor-based oxadiazinone was prepared by reaction of the N-nitroimine of d-camphor with (1R,2S)-norephedrine; the reduction of the resultant imine; N-nitrosation of the amine; reduction to the corresponding hydrazine and cyclization. The conformationa
- Squire, Michael D.,Davis, Ryan A.,Chianakas, Karah A.,Ferrence, Gregory M.,Standard, Jean M.,Hitchcock, Shawn R.
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p. 1047 - 1053
(2007/10/03)
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- Synthesis of 3,4,5,6-Tetrahydro-2H-1,3,4-oxadiazin-2-ones Employing a Metal Hydride and Diethyl Carbonate: An Alternative Cyclization Method over 1,1′-Carbonyldiimidazole
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A series of 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-ones have been synthesized from valine, leucine, ephedrine, and norephedrine. The synthesis is accomplished through a process of nitrosation, reduction, and cyclization. The cyclization protocol employed involves the use of a metal hydride (LiH or NaH) and diethyl carbonate rather than 1,1′-carbonyldiimidazole.
- Casper, David M.,Kieser, David,Blackburn, Jennifer R.,Hitchcock, Shawn R.
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p. 835 - 843
(2007/10/03)
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- Oxadiazinones as chiral auxiliaries: Diastereoselective aldol addition reactions of N3-glycolyl-3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-ones
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Asymmetric aldol reactions have been conducted with a series of N 3-glycolyl-3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-ones derived from (1R,2S)-ephedrine. These reactions afford the non-Evans syn-adducts in 43-97% yield and diastereoselectivities ranging from 62:38 to 99:1. Oxadiazinone substrates substituted with either the phenoxyacetyl or p-methoxyphenoxyacetyl groups gave the best results whereas the methoxyacetyl substituted oxadiazinone afforded diastereoselectivities that were modest.
- Hoover, Trisha R.,Hitchcock, Shawn R.
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p. 3233 - 3241
(2007/10/03)
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- Toward the development of a structurally novel class of chiral auxiliaries: Diastereoselective Aldol reactions of a (1R,2S)-ephedrine-based 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one
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(equation Presented) 8 examples Asymmetric aldol addition reactions have been conducted with (1R,2S)-ephedrine-derived 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one (2). Diastereoselectivities range from 75:25 to 99:1 for the formation of the crude non-Evan
- Casper, David M.,Burgeson, James R.,Esken, Joel M.,Ferrence, Gregory M.,Hitchcock, Shawn R.
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p. 3739 - 3742
(2007/10/03)
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- X-ray crystallographic and 13C nuclear magnetic resonance studies of 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-ones derived from ephedrine and pseudoephedrine
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3,4,5,6-Tetrahydro-2H-1,3,4-oxadiazin-2-ones derived from (1R,2S)-ephedrine and (1S,2S)-pseudoephedrine have been synthesized and their conformational properties have been examined. The ephedrine heterocycles 5-7a appear to favor one set of equilibrating
- Hitchcock, Shawn R,Nora, George P,Casper, David M,Squire, Michael D,Maroules, Christopher D,Ferrence, Gregory M,Szczepura, Lisa F,Standard, Jean M
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p. 9789 - 9798
(2007/10/03)
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