Domino Reactions Initiated by an Oxidation Reaction

Koo et al. [6] published the mechanistic evidence for this domino reaction. In addition, there are several reports available in the literature dealing with similar oxidative cyclizations to synthesize spiro-lactones [7], azoles [8], and isotwistanes [9]. 

Very recently, Donohoe et al. [11] used a similar domino process in the efficient synthesis of the ABC spiroacetal 23 ring system of pectenotoxin-4 24. In this reaction, triol 21 was converted into the bis-THF compound 22 with a yield of 69% using potassium osmate in an aqueous acetonitrile solution with pyridine-N-oxide (PNO) as a re-oxidant and a Lewis acid as promoter. The resulting compound 22 

When the same domino reaction was performed with N,N-dialkyl barbituric acid 29 as a Michael donor and catechol 25, the reaction did not provide the expected benzofuran derivatives. Interestingly, a new type of domino reaction took place, which gave polycycHc dispiropyrimidinone 30 in excellent yield. 

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