Functionalized aryllithium intermediates. A synthesis of benzocyclobutenes.

✍ Scribed by Peter D. Brewer; Jayaram Tagat; Charles A. Hergrueter; Paul Helquist

• Book ID: 104235868
• Publisher: Elsevier Science
• Year: 1977
• Tongue: French
• Weight: 128 KB
• Volume: 18
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)83571-1

✦ Synopsis

Benzocyclobutenes' have been found to be quite useful species for the synthesis of several types of compounds, including members of the alkaloid,* steroid,3 and polycyclic ter-penoid4 classes of natural products. The key step in each of these syntheses may be rationalized in terms of a (2+4) cycloaddition of an unsaturated compound to the quinodimethane resulting from ring-opening of the benzocyclobutene. 5 In consideration of the many uses of benzocyclobutenes, the need for efficient, convenient methods for preparing these compounds is readily apparent.6 MacNicol, ibid., 1893 (1975). Compounds la-d are conveniently available by routes discussed in detail elsewhere.6dy8 Chem. &., & 471 (1970). references to the uses of B. G. Beckmann, Tetrahedron C. A. Hergrueter, P. D. Brewer, J. Tagat, and P. Helquist, submitted for publication. All of these benzocyclobutenes, which are previously known compounds, 2,6a,b,d,g were identified by comparison of spectra with published data. THF is added to the reaction mixtures to effect more rapid cyclization. Alternatively, 3a-d may be obtained directly by performing the exchange reaction in THF.