ISSN:
0170-2041
Keywords:
Imidazolidinones, bromination of
;
Michaelis-Arbusov reaction
;
α-Aminoacrylic acid derivatives, chiral, nonracemic
;
Horner olefination with DBU/LiBr
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Preparation of Chiral Electrophilic Glycine and (E)-2,3-Dehydroamino Acid Derivatives from t-Butyl 2-t-Butyl-3-methyl-4-oxo-1-imidazolidinecarboxylate (Boc-BMI)Boc-BMI, the compound specified in the title, is brominated under radical-chain conditions (NBS/AIBN) to give trans-bromo-BMI 2, which is highly reactive in nucleophilic substitutions [see the 5-carbo- and -hetero-substituted (N, O, S, P) 2-t-butyl-3-methylimidazolidinones 4 - 23 and Tab. 1]. The substitutions occur preferentially with inversion of the configuration, the mechanism being not clear at all. - The Boc-BMI dimethyl phosphonate 23 (Michaelis-Arbusov product from 2) reacts with aldehydes (15 examples) to give preferentially (E)-5-alkylidene-imidazolidinones, chiral α-aminoacrylic acid derivatives which are available in either the R or the S form, see 24 - 38 (Tab. 2). Best yields and highest (E) selectivities (〉 25:1), with short reaction times, are obtained by using 1,8-diazabicyclo[5.4.0]undec-7-ene. (DBU)/LiBr in dry THF in a very special variant of the Horner olefination. α-Branched, racemic aldehydes may give alkylidene derivatives with efficient kinetic resolution (38). Some speculations are made about the mechanism and the observed stereochemical outcome of the reaction (I, J, K). A comparison is made with other chiral electrophilic glycine (A - C) and α,β-dehydroamino acid derivatives (D, E), as well as with other methods for the preparation of enantiomerically pure methylenedioxolan-, -oxazolidin-, and -imidazolidinones (H), containing an α,β-unsaturated carbonyl system.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.1991199101118
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