1122-26-5Relevant articles and documents
PREPARATION OF CHIRAL AMIDES AND AMINES
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Page/Page column 23, (2009/06/27)
This invention provides a convenient method for converting oximes into enamides. The process does not require the use of metallic reagents. Accordingly, it produces the desired compounds without the concomitant production of a large volume of metallic waste. The enamides are useful precursors to amides and amines. The invention provides a process to convert a prochiral enamide into the corresponding chiral amide. In an exemplary process, a chiral amino center is introduced during hydrogenation through the use of a chiral hydrogenation catalyst. In selected embodiments, the invention provides methods of preparing amides and amines that include the 1,2,3,4-tetrahydro-N-alkyl-1-naphthalenamine or 1,2,3,4-tetrahydro-1-naphthalenamine substructure.
COUNTERATTACK REAGENTS: THIOSILANES IN THE CONVERSION OF NITRO COMPOUNDS TO THIOHYDROXAMIC ACIDS AND THIOHYDROXIMATES
Hwu, Jih Ru,Tsay, Shwu-Chen
, p. 7413 - 7428 (2007/10/02)
Various primary nitro compounds were reacted sequentially with KH and Me3SiSSiMe3 in THF to give thiohydroxamic acids in 56-92 percent yields.By the same strategy, a thiohydroxamic acid was obtained in 50 percent yield by treatment of trans-β-nitrostyrene with i-PrSLi in THF and then with Me3SiSSiMe3.Reaction of primary nitro compounds with n-BuLi and then with MeSSiMe3 or PhSSiMe3 produced the corresponding thiohydroximates in 61-78 percent yields.Secondary nitro compounds were converted to oximes in 68-96 percent yields by reaction with KH and Me3SiSSiMe3 or MeSSiMe3 in THF or 1,4-dioxane.In these "one-flask" reactions, thiosilanes Me3SiSSiMe3, MeSSiMe3, and PhSSiMe3 acted as "counterattack reagents".
Stereoselective Reductions of Substituted Cyclohexyl and Cyclopentyl Carbon-Nitrogen ? Systems with Hydride Reagents
Hutchins, Robert O.,Su, Wei-Yang,Sivakumar, Ramachandran,Cistone, Frank,Stercho, Yuriy P.
, p. 3412 - 3422 (2007/10/02)
Reductions of 3- and 4-substituted cyclohexyl imines, iminium salts, and enamines (via iminium ions) with various hydride reagents reveal that while small reagents (NaBH4, NaBH3CN) favor axial approach as observed with the corresponding ketones, even moderately bulky reagents (i.e., acetoxyboranes) attack preferentially from the equatorial side.This is in direct contrast to the results observed for the same reagents with the corresponding ketones and is interpreted as implying that additional steric interactions induced by the nitrogen substituents encumber axial attack by substituted hydride reagents and force approach from the equatorial direction.The very bulky tri-sec-butylborohydride anion affords highly stereodiscriminating equatorial attack.Reductions of 2-alkylcyclohexyl and 2-alkylcyclopentyl imines and enamines also proceed with high stereoselectivity to give cis-2-alkyl cyclic amines with both hindered and unhindered reagents.This is interpreted to be the result of (1) augmented steric interactions between nitrogen substituents and equatorial 2-alkyl groups (1,3-allylic strain) which induces conformational changes to favor the axial 2-alkyl conformer and (2) hindrance toward equatorial approach by reagents induced by axial alkyl substituents.The result is that equatorial approach is favored with equatorial 2-alkyl conformers and preferential axial approach with axial 2-alkyl conformers, leading to stereoselective production of cis-2-alkylamines. trans-2-n-Propyl-4-tert-butylcyclohexanone is reduced by LiBH(sec-Bu)3 preferentially from the axial direction in contrast to the usual highly selective equatorial attack observed with other cyclohexanones.
