ワインレブアミド
ワインレブアミド (Weinreb amide) is amide of the N,O- dimethyl hydroxylamine.
I am used as a synthetic intermediate mainly when I derive a carboxylic acid derivative to aldehyde and ketone. This is technique reported in 1977 by Steven ワインレブ and others [1]; [2].
When I use lithium aluminum hydride (LAH) and a reducing agent such as hydrogenation bis(methoxyethoxy) aluminum sodium (with trademarks such as SMEAH, Red-Al) for carboxylic acid halide and ester, amide, hydride of 2 equivalents reacts, and I am resolved by alcohol (in the case of amide amine), and it is difficult to get aldehyde to produce on the way. Aldehyde may be provided when I use hydrogenation avian t- butoxyaluminum and hydrogenation Codonopsis ussuriensis till aluminum (DIBAL-H) which are a bulky reducing agent at low temperature, but I am influenced by the property of the substrate, and it cannot be said that it is common. When I get ketone by reacting a Grignard reagent, and substituting it for an alkyl group, a similar problem occurs.
This is because the metal alkoxide which hydride and an alkyl group of this 1 weight add this to a carbonyl group, and occurs releases an elimination group with instability easily, and it is to aldehyde and ketone. Because reactivity is easy to receive addition than that of carboxylic acid derivative as for the carbonyl group of aldehyde and ketone highly, I take first priority and react to alcohol and amine.
On the other hand, N-メトキシヘミアミナール which (in the figure R'M) including hydride and the Grignard reagent does nucleophilic addition in ワインレブアミド 1, and occurs is stabilized by two oxygen atoms making chelate structure 2 that metal coordinated of the metal alkoxide. Detachment, release of the amino group is hard to be caused by stabilized 2, and the addition reaction of the nucleophilic reagent of this 2 weight is controlled because it is hard to turn into aldehyde and ketone in the system. Adduct 2 is hydrolyzed by handling it with acid at the time of the reaction end and can get aldehyde and ketone 3 to be aimed for at the stage.
References
- ^ Basha, A.; Lipton, J. L.; Weinreb, S. M. "A mild, general method for conversion of esters to amides". Tetrahedron Lett. 1977, 18, 4171–4172. DOI: 10.1016/S0040-4039(01) 83,457-2
- ^ Nahm, S.; Weinreb, S. M. "N-methoxy-N-methylamides as effective acylating agents". Tetrahedron Lett. 1981, 22, 3815–3818. DOI: 10.1016/S0040-4039(01) 91,316-4
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