Alcohols Vilsmeier-Haack reaction

The 1,3-ditelluretane 88 is obtained as a minor product along with the 1,3-ditellurafulvene 89 by the reaction of phenylacetylide with tellurium followed by acidification with trifluoroacetic acid (Scheme 27) <2003TL2397>. In the reaction of trimethylsilylethynyl tellurolate, use of tifluoroacetic acid in /-butyl alcohol at — 20°C leads to the formation of the 1,3-ditelluretane 90, presumably via the telluraketene 91. Vilsmeier-Haack reaction on the crude ditelluretane 90 furnishes dialdehydes 27 and 92 in 10% yield. 1,3-Ditelluretanes 27 and 92 can be transformed into other derivatives, as shown in Scheme 28. An /. // mixture of 27 and 92 condenses smoothly with phosphorane to give diester product 93. The reaction with diesterdithiole phosphonate or dithiole phosphonate affords 1,3-ditelluretane derivative 94 or 95, respectively. 

Vilsmeier-Haack-type reaction provided the C ring of the Aspidosperma skeleton, and elaboration of the E ring was achieved by the addition of a radical generated from the xanthate derivative of the primary alcohol to give nonacyclic compound 111. The final steps for the completion of the total synthesis consisted of the formation of a lactone ring, which was achieved by oxidation of the tertiary amine with potassium ferricyanide,... 

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