The medicinal poteatfal of Eluorosteroids
192 prompted CF, additions to steroidal olefins, 2-4 but there has been no examination of their relative reactivities toward CFa, nor have these reactivities been related to those of the common alkenes. 5 Such information is important in synthetic planning, and we now report the first quantitative data for model steroidal olefins and related substrates. We studied olefins I-IV, X0-methyl-As -Z-o&alone a-ethylene acetal (V), and IO-methyl-A i(9) -2-octalone a-ethylene acetal (VI). CFa was generated from (CH.,),SnCF, and NaI in refluxing 1,2-dimethoxyethane13 or from C,H,HgCFa and NaI in refluxing benzene. l4 Additions of CFaa3 to Ifs, II,= or III proceeded in ~75% yield; the expected ~-difluorocyclopropanes50 were isolated by distillation (II) or by g.1.c. (Carbowax).l' Preparative-scale CF2 addition to IV was complicated by NaI (Ia ?) catalyzed isomerisation of IV to III, and subsequent addition of CFa to III. The adduct to IV was 20-30% of the product mixture but could be purified by g.1.c. on a Carbowax column at 160ยฐ.10*17 CR', and V gave 68% of VIIp and VIIa (ratio 250:1), separable by g.1.c. on a SE-30 column at lQO*. VIIB'o had m.p. 51.5-?13~; M" 258; *H n.m.r. 31.13, singlet, Wz-2 Hz (angular C.Ha)17*18. Minor adduct VII a had M+ 258, and 81.17, r s (angular CH,). The stereochemical assignments axe based on (1) analogy to 8 CF, additions to Aa steroidal olefinsXPa and to the B-endo-P addition of CFCl to V 8 , established by 0.6 Hz long-range coupling l9 of F and CH, observed in the 'H n.m.r. spectrum of the product, VII$ (exe-F = Cl); (2) similarity of the angular