L-Diethylamino-3-pentanone methiodide

The first use of this reagent in steroid synthesis was reported by Wilds in two communications, and some details are not clear. The reagent was generated in situ by the action of base on l-diethylamino-3-pentanone methiodide, presumably... 

The addition of rings B and A to ketone (277) was carried out by the same methods as in the case of its 5-methoxy analog (51) (see Scheme 94). Condensation with l-diethylamino-3-pentanone methiodide led to the tricyclic ketone (279), consisting of a mixture of double-bond isomers. The reaction of ketone (279) with l-diethylamino-3-butanone methiodide at —5°C enabled a mixture of epimeric ketols (278) to be obtained which, on boiling with sodium methoxide, gave the tetracyclic ketone (281). For the preparation of (281) from (277) without the isolation of the tricyclic ketone (279), methyl vinyl ketone has been used for the second condensation the over-all yield of (281) in two stages then amounted to 46% [28, 649, 955, 956]. 

The first stage of the synthesis, the preparation of the unsaturated cyclic ketone (140) is illustrated in Scheme 94. Here the starting material is 5-methoxy-2-tetralone (51), which was obtained in two stages from 2, 5-dihydroxynaphthalene with an over-all yield of 73% (Chapter HI, Scheme 56). Condensation of the tetralone (51) with l-diethylamino-3-pentanone methio-dide led to a mixture of the A - and A -tricyclic ketones (138). The next stage, the formation of ring A, can be carried out both with methyl vinyl ketone (yield 75%) and with l-diethylamino-3-butanone methiodide (yield 64%). The isolation of the tricyclic ketones (138) was not necessary, and by successively condensing the tetralone (51) with the diethylaminopen-tanone methiodide and methyl vinyl ketone it was possible to obtain the tetracyclic product (140) with an over-all yield of 34% [915, 916]. 

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