W-Bromobenzaldehyde

The following aldehydes may be condensed in similar manner to the above procedure to give the corresponding substituted 9-benzal-fluorene of the indicated melting point. o-Tolualdehyde, m.p. 109.5° p-chlorobenzaldehyde, m.p. 149.5° w-chlorobenzaldehyde, m.p. 90.5° and m-bromobenzaldehyde, m.p. 92-93°. 

Triethylsilane can also facilitate the high yielding reductive formation of dialkyl ethers from carbonyls and silyl ethers. For example, the combination of 4-bromobenzaldehyde, trimethylsi-lyl protected benzyl alcohol, and EtsSiH in the presence of catalytic amounts of FeCls will result in the reduction and benzylation of the carbonyl group (eq 32). Similarly, Cu(OTf)2 has been shown to aid EtsSiH in the reductive etherification of variety of carbonyl compounds with w-octyl trimethylsilyl ether to give the alkyl ethers in moderate to good yields. Likewise, TMSOTf catalyzes the conversion of tetrahydrop)ranyl ethers to benzyl ethers with Ets SiH and benzaldehyde, and diphenylmethyl ethers with EtsSiH and diphenylmethyl formate. Symmetrical and unsymmetrical ethers are afforded in good yield from carbonyl compounds with silyl ethers (or alcohols) and EtsSiH catalyzed by bismuth trihalide salts. An intramolecular version of this procedure has been nicely applied to the construction of cA-2,6-di- and trisubstituted tetrahydropyrans. ... 

The effect of hydrotropes on the crossed Cannizzaro reaction rate of benzaldehydes with aqueous formaldehyde was investigated [67]. In the presence of polyethyleneglycol-200 the reaction rate of w-phenoxybenzalde-hyde increases more than six-fold and the w-phenoxybenzyl alcohol is also obtained with higher selectivity. The enhancement of the reaction rate of m-bromobenzaldehyde is lower than that observed for m-phenoxybenzaldehyde but the reaction selectivity is higher. p-Anisaldehyde and p-chlorobenzalde-hyde show an intermediate behavior. The cationic surfactants cetylpyri-dinium chloride and cetyltrimethylammonium bromide (CTABr) favor the Cannizzaro reaction instead of the crossed Cannizzaro one. 

Kornblum aldehyde synthesis. 1-Iodoheptane added at 0-5° to a soln. of Ag-tosylate in acetonitrile protected from light, allowed to come to room temp, overnight, the resulting crude tosylate added at 150° to a freshly prepared mixture of NaHGOg and dimethyl sulfoxide through which Ng is passed, and cooled rapidly to room temp, after 3 min. at 150°-> n-heptaldehyde. Y 70% as the 2,4-dinitrophenylhydrazone.—Similarly at 100° during 5 min. p-Bromo-benzyl bromide p-bromobenzaldehyde. Y 76% as the 2,4-dinitrophenylhydrazone. F. e. s. N. Kornblum, W. J. Jones, and G. J. Anderson, Am. Soc. 81, 4113 (1959). 

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