Concise Synthesis of Diborylxanthenes

Abstract

A simple and efficient synthesis of a series of bidentate diborylxanthene derivatives is described.

Key words

boron - cross-coupling - Lewis acids - ipso-substitution - xanthene

References

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18

The reaction of lithiated 10 with Β-bromocatecholborane gave 3b in low yield (10%).

24

The ¹¹B NMR chemical shifts of 1c, 2c and 3c were not observed, probably because the signals were too broad.

25

It is not adequate to discuss the Lewis acidity by the values of ¹¹B NMR chemical shifts. See ref. 16.