Reactions of steroidal ketones with diazocyclopropane

Fluorinated β‐Diketones in Reactions with Diazocyclopropane Generated in situ

“…[36,37] Their versatility as synthetic blocks is clearly demonstrated by their capability to react with nucleophiles such as PhSeNa [38] and bases [39Ϫ41] such as R 2 NLi to give cyclopropanols, and to undergo ring-expansion to cyclobutanones on treatment with acidic reagents such as protonic acids, lithium or europium salts [39,42Ϫ44] or by thermal treatment. [45,46] It has been found that Grignard reagent-induced ring-expansion of oxaspiropentanes to cyclobutanols occurs through the intermediacy of a cyclobutanone, [47Ϫ48] and it has also been noted that the interaction of diazocyclopropane (3) generated in situ with the carbonyl groups of trispirodecanone [21] and of some ketosteroids [22,23] affords the corresponding cyclobutanones as a result of the isomerization of unstable oxaspiropentane intermediates. We thus studied the chemical transformations of the synthesized difluoro-and trifluoro-containing oxaspiropentanes 14Ϫ17 into the corresponding cyclobutanones and cyclopropanols under different reaction conditions.…”

“…[17] It is also known [20Ϫ23] that diazocyclopropane generated in situ reacts with some ketones to form oxaspiropentane derivatives or the products of their rearrangement. Treatment of 3 with acetone 8 thus gave dimethyloxaspiropentane 9 (Scheme 1), [20] while reactions between 3 and the carbonyl groups of trispirodecanone [21] and of steroids [22,23] afforded the corresponding oxaspiropentanes, which rearranged to cyclobutanone derivatives under the reaction conditions used. It should be noted that analogous reactions between cyclopropyl-ylides and carbonyl compounds [24Ϫ26] and the rearrangements of the resulting oxaspiropentanes have been used in strategies for the synthesis of some antibiotics and of antifungal, tumour-inhibitory and other biologically active substances.…”

Reaction of levoglucosenone with diazocyclopropane

“…5-8 Reactions of diazocyclopropane with unsaturated carbonyl compounds were described. 9, 10 However, the examples are limited by the reactions of diazocyclopropane with 3 acetoxypregna 5,16 dien 20 one and pregna 4,16 diene 3,20 dione. For these compounds, reactions with the carbonyl groups were observed along with formation of pyrazolines annulated to the ring D.…”

Reactions of diazocyclopropane with hydrogenated and cyclopropanated levoglucosenone analogs

“…Due to high reac tivity, diazocyclopropane reacts, like other diazoalkanes, with carbonyl compounds as well to form the respective oxaspiropentanes and homologation products of the ke tones. 5-8 Also the reactions of diazocyclopropane with unsaturated carbonyl compounds were described, but the known examples are limited to 3 acetoxypregna 5,16 dien 20 one and pregna 4,16 diene 3,20 dione 9, 10 where the reactions with the carbonyl groups were ob served along with 1,3 dipolar addition to the C=C bond of ring D. Recently, we have shown 11 that diazocyclo propane generated in situ from N cyclopropyl N nitroso urea under the action of bases reacts selectively with either the C=C double bond of levoglucosenone to form 1 pyrazoline (K 2 CO 3 , CH 2 Cl 2 , 5 °C) or the carbonyl group with selective formation of the respective oxaspiropentane (MeONa/MeOH, -30 °C) depending on the reaction conditions.…”