Selected data for 3: FAB-MS (M++1) 332.23180 C19H30O2N3 requires 332.23379; 1H NMR (60 MHz, CDCl3) 1.3 (s, 9H, p-t-but), 1.4 (s, 18H, 2xo-t-but), 7.4 (s, 2H, 2xm-H); 13C NMR (90.5 MHz, CDCl3) 157.3 (C=O), 148.0 (C1,C4), 141.1 (C2), 123.4 (C3-H), 35.5 (o-quart. C), 34.7 (p-quart. C), 31.4 (o and p-tert-butyl CH3); FT-IR max 2187 (m), 2135 (s), 2119 (m) (N3), 1788(m), 1744 (C=O), 1230 (C-O) cm¯¹.