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Synlett 2008(13): 1957-1960  
DOI: 10.1055/s-2008-1077962
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Selective O-Deallylation of o-Allyloxyanisoles

Roberto Sanz*a, Alberto Martíneza, César Marcosa, Francisco J. Fañanásb
a Área de Química Orgánica, Departamento de Química, Facultad de Ciencias, Universidad de Burgos, Pza. Misael Bañuelos s/n, 09001-Burgos, Spain
Fax: +34(947)258831; e-Mail: rsd@ubu.es;
b Instituto Universitario de Química Organometálica ‘Enrique Moles’, Universidad de Oviedo, C/Julián Clavería 8, 33006 Oviedo, Spain
Further Information

Publication History

Received 22 April 2008
Publication Date:
15 July 2008 (online)

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Abstract

o-Allyloxyanisoles are selectively and easily deallylated by treatment with sec- or tert-butyllithium at low temperature. The reaction is proposed to proceed through a tandem intermolecular carbolithiation-β-elimination process, which can also be considered an SN2′ attack of the organolithium on the allyl ether.

Key words

protecting groups - lithium - eliminations - phenols - ethers

    References and Notes

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9

The synthesis of the starting allylated ethers 8 was carried out under standard Williamson conditions (treatment of the corresponding phenol with allyl bromide and K2CO3 as base in refluxing acetone).

11

Ether 8a could be completely deallylated under the conditions reported by Bailey (t-BuLi, pentane, -78 ˚C to r.t., see ref. 5). We have also checked that 8a could also be deallylated by treatment with t-BuLi in Et2O at -78 ˚C by using 1 mL of solvent per mmol of 8a.

15

Thioether 13 was prepared from 2-methoxythiophenol by its treatment with NaOH and allyl bromide in water.

16

A small amount of the expected 2-methoxythiophenol could be detected in the crude product of the reaction.

17

Although treatment of 16 with s-BuLi also afforded a mixture of 17 and 18 as main products, in this case 2-methoxymethyl phenol was also obtained as a minor product.