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 Δ 5 ‐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 D 3 ‐ p ‐nitrobenzoate from the vitamin‐D 3 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 C 6 H 10 (X) (Y) (X = N 3 , Cl, Y = N 3 , J) from the corresponding trans ‐1,2‐disubstituted cyclohexanoles C 6 H 10 (X) (OH) (X = N 3 , Cl). The synthesis of the compounds 14a ‐ 15d can be regarded as representative of this new useful methodic principle.