Enantioselektive 1,4‐Additionen von metallorganischen Verbindungen an konjugierte Systeme im chiralen Medium DDB

Abstract

Enantioselective 1,6additions of organometallic compounds to conjugated systems in the chiral medium DDB') SummaryThe chiral methoxyamine DDB is used as a cosolvent to add achiral Li-, Cu-, and Zn-organic compounds enantioselectively to prochiral P-carbon atoms of a , B-

Conjugate additions of grignard reagents to α,β-unsaturated ketones mediated by diamine zinc(II)monoalkoxides

“…The enantioselectivity is comparable to results of the addition of lithiumtrialkylzincates to cyclohexenone using S,S-1,4-dimethylamino-2,3-dimethoxybutane as a chiral co-solvent. (14) We propose that an alkoxy-(diamine)-monoalkylzinc complex is formed in analogy with recently proposed structures of zinc-catalysts for 1,2-additions. (2) This complex binds one equivalent of Grignard compound to form the active reagent for 1,4-additions.The result with KOtBu and 8 (entry 2) as well as the results with l-menthoxide as chiral nontransferable ligand in TMEDA.ZnCl 2 mediated additions (entry 3,4) support this mechanism.…”

Asymmetric Michael Additions to Nitroalkenes

“…In pioneering experiments it was shown [72] that the readily available C 2 -symmetric 2,3-dimethoxy-1,4-bis(dimethylamino)butane (S,S)-DDB (141), used as a cosolvent in a 1:1 ratio with pentane, was responsible for the enantioselective addition of Ph 2 Zn to nitropropene. The reaction proceeds in good yield giving an enantiomerically enriched product 140 (Scheme 48).…”

2.06 Formation of Enolates

“…204 Lithium triorganozincates, R 3 ZnLi, are known to effect 1,4-addition of alkyl groups to α,β-unsaturated ketones (Scheme 56). [205][206][207][208] They are an attractive alternative to the lithium diorganocuprates because of their solubility and thermal stability. A disadvantage of this method is that only one alkyl ligand can be transferred; the other two are lost.…”