Reaktionen mit phosphororganischen Verbindungen. XLI[1]. Neuartige synthetische Aspekte des Systems Triphenylphosphin‐Azodicarbonsäureester‐Hydroxyverbindung

Abstract

New preparative methods using triphenylphosphine‐diethyl‐azodicarboxylate‐hydroxycompound.The present paper deals with new preparative methods by which the system of triphenylphosphine‐diethylazodicarboxylate‐hydroxycompound is treated with many nucleophiles. On one side, the transformation of 5α‐cholestane‐3β‐ol to the 3α‐substituted derivatives 2a‐2e (Scheme 1) by hitherto unregarded nucleophiles like azide, cyanide, thiocyanate, trifluoroacetate and thiophenoxide is shown. Further examples demonstrate the great applicability of the reaction in the case of sensitive substrates. Cholesterol (5) is transformed to the 3α‐derivative 6a without any neighbouring group participation by the Δ5‐double bond. The analogous transformation of the hydroxysteroides 7 and 9 to the corresponding 3α‐substituted compounds 8a and 10a represent further examples to be noted. Noteworthy is also the formation of the epi‐vitamine D3‐p‐nitrobenzoate from the vitamin‐D3 itself. On the other side the sources for nucleophils require special consideration. Scheme 1 demonstarates that the anions of phosphonium salts can be used as the nucleophils as is shown by the preparation of the derivatives 2a, 2c, 2f, 2h and 2i from 5α‐cholestane‐3β‐ol (1). From scheme 2 one can see the very useful preparative fact (1→2f, 2g, 2h, 21 and 2m) that alkylhalides, alkylsulfates and alkylsulfonates can be used for supplying of the corresponding nucleophile. The possibility of a direct tosylation of a chiral hydroxycompound with inversion of configuration‐as it is shown by transformation of (S)‐2‐butanol to the tosylate, obtained also from (R)‐2‐butanol and tosylchloride is a further is a further remarkable point. The absence of neighbouring group effects allows also to prepare cis‐1, 2‐ disubstituted cyclohexane compounds type C6H10 (X) (Y) (X = N3, Cl, Y = N3, J) from the corresponding trans‐1,2‐disubstituted cyclohexanoles C6H10 (X) (OH) (X = N3, Cl). The synthesis of the compounds 14a‐15d can be regarded as representative of this new useful methodic principle.