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Recent advances in the ring expansion of cyclobutanols, oxetanols, and azetidinols

2020; Elsevier BV; Volume: 61; Issue: 14 Linguagem: Inglês

10.1016/j.tetlet.2020.151695

1873-3581

Philipp Natho, Lewis A. T. Allen, Philip J. Parsons,

Sulfur-Based Synthesis Techniques

The number of developed methodologies for the ring expansion of cyclobutanol rings to five, six and seven-membered rings has increased significantly over the last six years. In this timeframe, the semipinacol rearrangement of vinyl-group containing cyclobutanols to cyclopentanones has been advanced under photoredox and electrochemical conditions, enabling the concomitant introduction of a wide array of functional groups. The expansion to 1- and 4-tetralones has been achieved for the first time under transition-metal-free conditions and even expansion to seven-membered rings has been demonstrated under rhodium catalysis. In this article, we will critically discuss the scope, application and mechanistic studies of procedures published since 2013, and provide a short outlook on the emerging potential for further development in this area.