By Diego Savoia (auth.), Marc Lemaire, Pierre Mangeney (eds.)
The use of phosphine derivatives has traditionally brought about the large improvement of catalysis (both non-asymmetric and asymmetric). even though the chemistry of amines is extra documented, using nitrogen-containing ligands purely seemed lately. however, over the last ten years, the consequences describing chiral diamine arrangements and their makes use of in uneven catalysis and synthesis are expanding swifter than their phosphorus opposite numbers. The reader will locate during this quantity the newest equipment for the synthesis of chiral diamines in addition to their functions in uneven catalysis of CC bond formation. specific recognition could be given to spartein and derivatives of such diamines. lately, the actual houses and the chemistry of amines allowed to procure catalysts effortless to split and recycle and new varieties of ligands corresponding to diaminocarbenes, ureas and thioureas. eventually, the complexing houses of a few diamines allowed the formation of complexes with chirality "at the steel " that is of significant theoretical curiosity and provides a variety of capability applications.
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Extra resources for Chiral Diazaligands for Asymmetric Synthesis
Example text
Organolithium–cerium trichloride reagents are the reagent of choice, as they react at – 100 ◦ C in THF to afford the corresponding hydrazines 273 with quantitative yields and high diastereoselectivity, the syn diastereomers being prevalent. A drawback of this reaction is that the organometallic reagents must be used in large excess (8 equiv) [135, 136] (Scheme 44). ), subsequent protection of the crude products with a large excess of di-tert-butyl dicarbonate or benzyloxycarbonyl chloride and final purification by chromatography.
Conversely, lithium enolates of N-benzylidene-α-substituted-α-amino acid methyl esters added to the si face of aryl sulfinimes (S)-97, presumably by a concerted mechanism, when allowing the temperature to rise from – 78 to 4 ◦ C, affording the imidazolidines (R,R)-98 with high diastereoselectivity [54] (Scheme 16). Next, cleavage of the imidazolidine ring and removal of the sulfinyl N substituent was accomplished by treatment with phosphoric or trifluoroacetic acid, to give the 2,3-diamino esters (2R,3R)-99.
The receptor 221 has been also synthesized by this route [103] (Scheme 33). The Leuckart–Wallach reaction is the oldest method of reductive amination of carbonyl compounds. It makes use of formamide, formic acid or ammonium formate at high temperature. The final product is a formamide derivative, which can be converted to an amine by reduction or hydrolysis. The method has been applied to the preparation of 1,2-diamines with a norbornane framework, which are interesting rigid analogues of 1,2diaminocyclohexanes.