Synthesis of steroidal derivatives containing substituted, fused and spiro pyrazolines

• The synthesis of novel pyrazoline steroids is described.
• We report the synthesis of the first spiro-steroidal pyrazoline at C-22.
• The cycloaddition of hydrazine to α,β-unsaturated ketones was the key step.
• The mechanism of reaction was established by the isolation of an intermediate.
• The structures of new compounds were confirmed by NMR studies.

An efficient and facile synthesis of fused, substituted and spiro pyrazoline steroid derivatives through a cycloaddition reaction of different α,β-unsaturated ketones with hydrazine acetate in acetic acid is reported. Depending on the starting material, the ring closure reaction provided a mixture of two steroidal pyrazoline epimers that were separated and studied by NMR techniques. In one case it was possible to isolate and characterize the hydrazone derivative as the reaction intermediate, which confirms the mechanism proposed in the literature [11,25,26].

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