Highly diastereoselective and enantioselective preparation of homoallylic amines: application for the synthesis of beta-amino acids and gamma-lactams.
Reactions of N-silyl- and N-aluminoimines with B-allyldiisopinocampheylborane in the presence of methanol, followed by oxidative workup furnished homoallylic amines in good yields and high ee. A 11B NMR spectroscopy study revealed that the reactions do not proceed, even at room temperature, unless a molar equivalent of water or methanol is added. The first reagent-controlled asymmetric crotylboration and alkoxyallylboration of aldimines furnishing beta-methyl or beta-alkoxy homoallylic amines in very high diastereoselectivity and enantioselectivity are reported herein. Crotylboration and alkoxyallylboration of imines proceed only with the "allyl"-boron "ate" complexes, instead of the "allyl"-dialkylboron reagents used with aldehydes. The addition of methanol is necessary for these reactions as well. Application of this methodology for the conversion of representative nitriles to beta-amino acids in two steps has been described. Additionally, a procedure for the preparation of chiral delta-amino alcohols and gamma-lactams from nitriles is also reported.
Ramachandran
P Veeraraghavan
PV
Herbert C. Brown Center for Borane Research, Department of Chemistry, Purdue University, West Lafayette, IN 47907-2084, USA.
Burghardt
Thomas E
TE
D000588:Amines / Q000737:chemistry*; D000596:Amino Acids / Q000138:chemical synthesis*; D007769:Lactams / Q000138:chemical synthesis*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism
D000588:Amines; D000596:Amino Acids; D007769:Lactams