2- allyl-6-bromophenol

Allyl-6-bromophenol, the precursor of prostacyclin analogues, is usually prepared by the way as shown in Scheme 3 (ref. 13). 

In the above section we describe the convenient preparation of 2-allyl-6-bromophenol without any bromine adduct. It seems that these results are not able to be explained by the mechanisms via bromine molecule, which are described later. 

The phenolic oxygen on 2-allyl-4-bromophenol (7) readily underwent oxypalladation using a catalytic amount of PdCl2 and three equivalents of Cu(OAc)2, to give the corresponding benzofuran 8. This process, akin to the Wacker oxidation, was catalytic in terms of palladium, and Cu(OAc)2 served as oxidant [17]. Benzofuran 10, a key intermediate in Kishi s total synthesis of aklavinone [18], was synthesized via the oxidative cyclization of phenol 9 using stoichiometric amounts of a Pd(II) salt. 

The Pd-catalyzed AAA reaction of bromophenol 54 and allylic carbonate 72 in the presence of chiral bis-phosphine ligand 73 gave aryl ether 74 in 72% yield with 88% ee (Scheme 15). After protection of the aldehyde function in 74 as a dimethyl... 

Figure 13.3.8. Effect of the volume ratio of water to chlorobenzene on the conversion 1.568 g of 4-bromophenol, l.OgofKOH, 0.7gof allyl bromide, 0.2 g of TBAB catalyst, 50 mL of chlorobenzene, 50°C. (Adapted from Ref. [135], by permission.)...

In addition to the palladium catalysts mentioned, other transitional metal catalysts were explored and applied in this transformation as well. In 1995, Dunach and Olivero studied the nickel-catalyzed electrochemical reductive deprotection of allyl ethers. Among the various substrates, allyl-o-halogenophenols were tested as well. 2-Chlorophenol was produced from allyl-o-chlorophenol phenol was produced from allyl-o-bromophenol while 3-methyl-2,3-dihydrobenzofuran (33%) was produced from allyl-o-iodophenol together with phenol (52%). 

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