Favorskii rearrangement of 23-oxo-3-epi-smilagenin acetate induced by iodosobenzene
Graphical abstract
Treatment of (25R)-23-oxosapogenin with diacetoxyiodobenzene in KOH/MeOH led to F-ring contraction via Favorskii rearrangement.
Section snippets
Acknowledgments
We thank Dirección General de Asuntos del Personal Académico (DGAPA-UNAM) for support via project IN200105 and Professor Benjamin Ruiz Loyola (UNAM) for providing laboratory facilities. We are also indebted to Rosa I. del Villar Morales and Georgina Duarte Lisci (USAI-UNAM) for registering all NMR and Mass spectra.
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Synthesis of α-benzylated amides via electrocatalytic Favorskii rearrangement of 1, 3-diarylacetones
2018, TetrahedronCitation Excerpt :When α-haloketones are treated with a nucleophilic base, carboxylic acids, esters and amides are usually obtained as reaction products via the C-C skeletal rearrangement. Besides base, by the employment of hypervalent iodine reagents,2 acid,3 enzyme,4 photochemistry5 or electrochemistry,6 some novel Favorskii rearrangements have been also developed. To date, some reviews by Butkus7 and Yus8 discussed synthetic applications of this rearrangement.
Regioselective hypervalent iodine-induced Favorskii rearrangement of 3-oxo-5β-steroids
2016, SteroidsCitation Excerpt :Provided that 2a can be produced by both, the CPM and the SBM, the 9/1 ratio in which 2a predominates over 2b, suggests that in this particular case both mechanisms occur simultaneously, although SBM predominates. On the other hand, the absence of α′-protons in compounds 3 and 5 (Eqs. 2 and 3), makes the exclusive participation of SBM mandatory and justifies the observed regioselectivity [16,17]. Examination of the literature indicates that when iodine III compounds are employed, FR of cyclic ketones is only a deviation of the more generally observed α-hydroxylation-ketalization course (Scheme 3, Eq. 4) [18].
Diacetoxyiodobenzene-mediated synthesis of unnatural furospirostane sapogenins derived from diosgenin and tigogenin
2013, SteroidsCitation Excerpt :The conversion of tetrahydropirane F-ring into a tetrahydrofurane produces significant changes in the NMR signals of the nuclei placed in the side chain. In agreement with our previous report [17], the NMR spectra of the rearranged compounds 7a-b show the 1H and 13C NMR signals corresponding to the CH3O group at 3.71–3.72 and 51.8 ppm, respectively. In addition, the 13C signal of the spiroketal at C-22 (119.3 ppm) and the carboxyl at C-231 (172.50 ppm) as well as the signal of C-25 (72.4–72.5) which bears the diastereotopic pair H-25 pro-S (4.01–4.02 ppm) and H-25 pro-R (3.46–3.48 ppm) characterize the NMR spectra of the rearranged compounds 7a-b.