Dotz natural product synthesis

The synthetic value of the Dotz reaction has for example been demonstrated by the synthesis of vitamin Ki(20) 10 (simplified structure). This natural product has been prepared synthetically from the chromium carbene complex 8 and the alkyne 9 in two steps the second step being the oxidative decomplexation to yield the free product 10 ... 

P. Quayle and co-workers utilized the Dotz benzannulation reaction for the synthesis of diterpenoid quinones." The authors developed a novel synthetic approach to 12-O-methyl royleanone using a simple vinyl chromium carbene complex along with a disubstituted oxygenated acetylene. The bicyclic hydrazone was converted to the corresponding vinyllithium derivative by the Shapiro reaction and then functionalized to give the desired crude Fischer chromium carbene complex. The benzannulation took place in refluxing THF with excellent regioselectivity, and the natural product was obtained in 37% overall yield from the hydrazone. 

R, R2 H) depends almost entirely on the difference in size of the substituents R, and R2 and rarely on electronic effects [159c]. The high regioselectivity and functional group tolerance predestines the Dotz reaction for the synthesis of various natural products [159,161 b, c]. 

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