[3,3]-sigmatropic Claisen rearrangement: a rapid access to Phenylpropenes and Lignan structures.

Phenylpropenes or allylbenzenes derivatives are the skeletons of many biologically important natural products as gingerol, eugenol, chavicol, safrole and estragole (1). They are also precursors of Lignans and Stegane structures which are studied for their important activities (2). In this work we report a rapid and efficient methodology to obtain various phenylpropenes 1 performing a [3,3]-sigmatropic Claisen rearrangement of compounds 2 (3). The protected phenols could be easily prepared from substrates 3 with an allylation reaction on the corresponding free hydroxyl group. (Figure 2). With this synthetical approach we are able to synthesize the 1,2,3,4-tetramethoxy-5-(2-propenil)benzene, an antibacterical natural product (4), in only 4 steps and 58% overall yield. (1) Koeduka, T. Plant Biotechnol. 2014, 31, 401–407. (2) Chang, J.; Reiner, J.; Xie, J. Chem. Rev. 2005, 105, 4581–4609. (3) Tripathi, S.; Chan, M.-H.; Chen, C. Bioorg. Med. Chem. Lett. 2012, 22, 216–221. (4) Trikojus, V. M.; White, D. E. J. Chem. Soc. Resumed 1949, 436–439.