STRUCTURE OF 2,3-DIHYDRO-1-METHYLQUINOLIN-2-SPIRO-2'-INDIAN-3'-SPIRO-2''-(1'',3''-DITHIANE)-4,1'-DIONE

C21H19NO2S2, M(r) = 381.51, monoclinic, C2/c, a = 24.911 (4), b = 10.028 (2), c = 17.042 (2) angstrom, beta = 121.367 (8)-degrees, V = 3634.8 (9) angstrom3, Z = 8, D(x) = 1.394 g cm-3, lambda(Cu Kalpha) = 1.54178 angstrom, mu = 27.25 cm -1, F(000) = 1600, T = 295 K, R = 0.036 for 2385 observed [I/sigma(I) greater-than-or-equal-to 3] reflexions. The dithiane ring adopts a flattened chair conformation; in the dihydroquinolone ring both the N-methyl and the carbonyl group are essentially coplanar with the benzene ring; the spiro junction is made with the indanone carbonyl pseudo equatorial and the spirodithiane linked pseudo axially. The structure shows the novel result of attempted tandem addition (nucleophile then electrophile; at 2-C then 3-C positions in a quinolin-4-one) of methyl 2-formylbenzoate dithiane anion to 1-methylquinolin-4-one. A mechanistic explanation is suggested.