Photolytic reactions of chromium aminocarbene complexes. Conversion of amides to .alpha.-amino acids

• Published in: Journal of the American Chemical Society Vol. 112; no. 6; pp. 2264 - 2273
• Main Authors: Hegedus, Louis S, Schwindt, Mark A, De Lombaert, Stephane, Imwinkelried, Rene
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 01.03.1990; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Exact sciences and technology; General and physical chemistry; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Physical Sciences; Science & Technology; Carbene; Transition metal Carbonyl Complexes; Aminoester; Photolysis; Chromium Carbonyl Complexes; Methanol
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja00162a029

A variety of tertiary amides was converted to chromium aminocarbene complexes by reaction with Na2Cr(CO)5 and trimethylsilyl chloride. Photolysis of these carbene complexes in methanol or tert-butyl alcohol solvent produced .alpha.-amino esters in good to excellent yield. Aminocarbene complexes containing chiral oxazolidine groups were synthesized and photolysed in alcohol to produce chiral .alpha.-amino esters in 50-93% de. Pentacarbonyl[(dibenzylamino)(methyl)carbene]chromium(0) was prepared in high yield by the N-benzylation of the corresponding monobenzyl amino complex. Base-assisted alkylation of the methyl group with a variety of halides followed by photolysis in methanol produced the alkylated alanine methyl ester in excellent overall yield. Other aminocarbene underwent similar reactions. With chiral, optically active aminocarbene complexes, the alkylated alanine derivative was produced with high diastereoselectivity.