Applications de la reaction de ritter en serie steroide—I

Ritter Reaction Mediated by Bismuth(III) Salts: One-Step Conversion of ­Epoxides into vic-Acylamino-Hydroxy Compounds

“…Therefore a large use in organic synthesis for this process should be found. Spectroscopic data for the trans-acylamino-hydroxy compounds 2, 9 4, 9 8, 9 10, 17 11, 12 13, 9 14 18 are in agreement with those reported in literature. 19 The compound 6, a new steroid compound, was fully characterized with 1 H NMR, 13 C NMR, IR (ATR), ES-MS and elemental analysis.…”

“…In the presence of either BF 3 ·OEt 2 or HClO 4 , 5a,6a-, 5b,6b-and 2b,3b-epoxysteroids gave trans acetamido-alcohols. 9 In another study it was found that in all the four epoxides studied (4a,5a-and 4b,5b-epoxides with a hydroxyl or acetate at C 3 ) in the presence of HClO 4 , the product invariably results from the addition of the nitrogen atom at C 5 . These results were explained on the basis of the development of a partial positive charge on the more substituted carbon of the epoxide which would lead to substitution at C 5 .…”

1,2-Amino Alcohols and Their Heterocyclic Derivatives as Chiral Auxiliaries in Asymmetric Synthesis

“…There are a number of means to achieve this with simple alkenes, but the one with most promise is that based on the use of manganese−salen. − With unsymmetrical epoxides, the regioselectivity can be controlled through reagent choice . Nucleophilic attack tends to prefer reaction at the least hindered center with concurrent inversion, as observed with primary and secondary amines (Scheme ), − and their group I or II metal salts, ,− while group IV and V amine compounds tend to provide reaction of the nitrogen nucleophile at the more hindered center. −

16

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Starbon®400-HSO3: A green mesoporous carbonaceous solid acid catalyst for the Ritter reaction

“…Using steroid compounds with epoxides fused to rings A or B, the Ritter reaction proceeds through trans-diaxial ring opening of the epoxide to afford vic-N-acylamino-hydroxy steroids. Corrosive acid catalysts, such as BF 3 ·OEt2 [15,16,17], gaseous BF 3 [15], HClO 4 [16,18,19], SnCl 4 [20] and p-toluenosulfonic acid [20] have been reported for this transformation. More recently, a new process using bismuth(III) salts as ecofriendly catalysts has been described for the Ritter reaction of epoxysteroids [21,22].…”