Equilenin ketone oxalylation

The reaction of diethyl oxalate with ketones in the presence of sodium ethoxide, or other bases, has been used extensively examples are given in Scheme 66. Reaction may occur with esterketone ratios of 1 1, 2 1, or 1 2, but only the 1 1 case finds substantial use in modem synthetic practice. Frequently the a-oxalyl ketone is thermally decarbonylated to give the 3-heto ester.An early example of this was provided by Bachmann s synthesis of equilenin. The mechanism of this reaction has teen examined labeling studies showed that it was the ester carbonyl that was eliminated. The intact oxalyl group has teen used as a directing group in steroid methylation while, more recently, 2-oxalylcyclohexanone has provided a route to (R)-(-)-hexahydromandelic acid (Scheme 67). The products of acylation of suitable acyclic ketones can cyclize to form (enolic) cyclopentane-1,2,4-triones (equation 39). ... 

The first total synthesis from Butenandt s ketone (6) was achieved by Bachmann et al. in 1939 [137, 147], who obtained racemic equilenin (23) (Scheme 2). The introduction of the atom into the ketone (6) was carried out by oxalylation, that of the 0 3 atom by angular methylation, and that of the and atoms by the Reformatskii reaction. The closure of ring D was effected by Dieckmann cyclization. 

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