title: Asymmetric Carbamoyl Anion Additions to Chiral N-Phosphonyl Imines via the GAP Chemistry Process and Stereoselectivity Enrichments.
abstract: Carbamoyl anions were found to smoothly react with chiral N-phosphonyl imines in toluene at -78 °C to r.t. using LiHMDS as the base. Group-assisted purification (GAP) has been utilized to give the pure amides without using column chromatography or recrystallization. The asymmetric reaction resulted in chiral N-phosphonyl amino amides with good to excellent yields (71-99%) and good crude diastereoselectivities (dr 84:16-95:5). In this GAP procedure, the crude solids are washed with diethyl ether to afford the pure products, as revealed by (1)H NMR analysis; GAP washing consistently increases the diastereopurity of the products, resulting in excellent diastereoselectivities, often with final dr > 99:1. Interestingly, the diastereoenriched products can be obtained either in the ether solution or as the suspended solid, depending on the substrate.
authors.affiliation: †Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States.
authors.forename: Cole W
authors.initials: CW
authors.lastname: Seifert
authors.affiliation: †Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States.
authors.forename: Suresh
authors.initials: S
authors.lastname: Pindi
authors.affiliation: †Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States.
authors.forename: Guigen
authors.initials: G
authors.lastname: Li
mesh_terms: D000577:Amides / Q000138:chemical synthesis* / Q000737:chemistry; D000838:Anions / Q000737:chemistry; D007097:Imines / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D000577:Amides; D000838:Anions; D007097:Imines