Yield 54%.
M.p. 97–98 ºC (lit. 95 ºC; Ref. 2)
Rf 0.56 on SiO2 in 1:1 ethyl acetate:hexane
1H NMR (300 MHz, CDCl3) δ 2.60 (s, 4H, CH2), 1.29 (s, 6H, C2-CH3), 0.98 (s, 6H, C5-CH3).
13C{1H} NMR (75 MHz, CDCl3) δ 210.6 (2C, C=O; C1, C3), 60.5 (1C, Cq; C2), 51.2 (2C, CH2; C4, C6), 30.8 (1C, Cq; C5), 28.6 (2C; C5-CH3), 22.3 (2C; C2-CH3). Atom assignments are based on DEPT135 and HMBC analyses.
ESI-MS m/z calcd for [M+Na]+ 191.1043, found 191.1042.
IR (KBr, cm–1): ν(C–H) 2969, 2936, 2874; ν(C=O) 1722, 1686.