Grundmann s ketone

The Trost synthesis of calcitriol (3) is shown in Scheme 5. In a Wittig reaction, the hydroxylated Grundmann s ketone 26 (obtained by partial synthesis) is transformed into the alkenyl bromide 27 with astonishingly high diastereoselec-tivity ElZ >50 1). The chiral enyne 29, which is needed as the second building block for the coupling step, is prepared from the aldehyde 28... 

Grundmann s aldehyde synthesis also starts from acid chlorides. The latter are converted by way of the diazo ketones or acetoxy ketones into the glycols, which are subjected to cleavage by lead tetraacetate. <%,/ -Unsaturated aldehydes cannot be obtained by this method.457... 

This reaction was initially reported by Grundmann in 1936. It is the conversion of acyl chloride into aldehyde with the exact same carbon skeleton via the following consecutive steps a) treatment of acyl chloride with diazomethane to form a ketone, (b) conversion of such a ketone into ketol acetate with acetic acid, (c) reduction of ketol acetate with aluminum isopropylate, and d) hydrolysis and oxidation with lead tetraacetate. This method is especially useful in the preparation of aliphatic aldehydes with methylene-interrupted double bond(s). Although polymers might form in the preparation of highly unsaturated aldehydes during the reduction with aluminum isopropylate, the reduction from lithium aluminum hydride can eliminate such drawbacks. ... 

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