Synthesis and structures of novel chiral lithium amidinates and mono- and di-lithium (1R,2R)-(−)-1,2-(NHSiMe3)2C6H10

Abstract

Four lithium salts derived from (1R,2R)-1,2-diaminocyclohexane are described. After the resolution of 1,2-diaminocyclohexane (DACH), (1R,2R)-(−)-1,2-(NHSiMe₃)₂C₆H₁₀ (1) was prepared from the (R,R) enatiomer by reaction with LiBuⁿ and Me₃SiCl. Treatment of 1 with one equiv. of LiBuⁿ gave the single lithium salt (1R,2R)-(−)-1-Li(NSiMe₃)-2-(NHSiMe₃)C₆H₁₀ (2). Double deprotonation of 1 with two equiv. of LiBuⁿ yielded the dilithium salt Li₂[(1R,2R)-(−)-1,2-(NSiMe₃)₂C₆H₁₀] (3). The addition reaction of 2 or 3 with PhCN gave (1R,2R)-(−)-1-Li[NC(Ph)N(SiMe₃)]-2-(NHSiMe₃)C₆H₁₀ (4) and Li₂[(1R,2R)-(−)-1,2-{NC(Ph)N(SiMe₃)}₂C₆H₁₀] (5) respectively. Crystallographic studies and comparison of these lithium salts with β-diketiminates exhibit some noteworthy features.