Synthesen von 3‐Hydroxy‐4‐methyl‐3‐cyclobuten‐1,2‐dion (Methylmoniliformin)

Syntheses of 3‐Hydroxy‐4‐methyl‐3‐cyclobutene‐1,2‐dione (Methylmoniliformin) New routes to 3‐hydroxy‐4‐methyl‐3‐cyclobutene‐1,2‐dione(9), the lowest homologue of the mycotoxine moniliformin are described. A common feature of all pathways is the synthesis of methylcyclobutanes having the oxidation level 6. Precursors, which are easily transformed to9by acid catalyzed hydrolysis, include [2+2]‐cycloadducts ofin situgenerated methyl ketene to tetraethoxyethylene and [2+2]‐photocycloadducts of dichlorovinylenecarbonate with 1,1‐dichloro‐1‐propene. The acid hydrolysis of [2+2]‐cycloadducts of chlorotrifluoroethylene toN, N‐diethyl‐1‐propynylamine yields the diethylamide of9 (=22)in 50% overall yield. In addition, a convenient one‐pot‐two‐steps synthesis of a new electronrich ethylene, 1,1,2‐triethoxy‐2‐trimethylsilyloxy‐ethylene(11), is described.