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Diastereoselective Michael Additions of Chiral Imidazolidines to Trityl Enones
Author(s) -
Seebach Dieter,
Pfammatter Elmar,
Gramlich Volker,
Bremi Tobias,
Kühnle Florian,
Portmann Stefan,
Tironi Ilario
Publication year - 1992
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.1992199201188
Subject(s) - chemistry , diastereomer , steric effects , adduct , reagent , michael reaction , medicinal chemistry , stereochemistry , organic chemistry , catalysis
The enolates A and C of t ‐butyl ( R )‐2‐ t ‐butyl‐3‐methyl‐4‐oxo‐1‐imidazolidinecarboxylate ( 1 , Boc‐BMI) and of 1‐ t ‐butyl 5‐methyl (2 R ,5 S )‐2‐ t ‐butyl‐3‐methyl‐1,5‐imidazolidinedicarboxylate ( 3 ) and t ‐butyl ( R )‐2‐ t ‐butyl‐5‐lithio‐3‐methyl‐1‐imidazolidinecarboxylate ( B , from 2 ) add in a Michael‐type reaction to trityl enones ( E, 4, 5 ). With one exception (product 8 ) a single diastereoisomer is formed (≫98% ds). — In two cases ( 6, 10 ), the crystal structures of the products are determined by X‐ray diffraction. The steric course of the reactions (the relative topicity is unlike with the enolates) is discussed and compared with that of other conversions of the same reagents. — The trityl groups of two adducts ( 8 and 9 ) are cleaved off by treatment with LiBH 4 /cat. LiBHEt 3 to give diaminopentanol derivatives ( 12 and 13 ).