A,p-ethylenealdehydes

Arylcarboxylic acids. BaMn04 added to a stirred soln. of 4-methoxybenzaldehyde in methylene chloride at 36°, and stirring continued for 14 h - 4-methoxybenzoic acid. Y 77%. Aliphatic aldehydes gave a polymeric residue, a,p-ethylenealdehydes gave low yields, and heterocyclic aldehydes remained unoxidised. F.e.s. R.G. Srivastava, P.S. Venkataramani, Synth. Commun. 18, 2193-200 (1988). 

M -butyllithium in hexane added dropwise at —40° to a soln. of 2-propenyl-l,3-dithiane in ether, stirred for 20 min, cooled to —78°, 1 eq. BF3-etherate in ether added dropwise followed by propylene oxide, and worked up after 20-60 min. (t.l.c. monitoring) product. Y 95%. This is part of a 3-step preparation of functionalized a,p-ethyleneketones from a,p-ethylenealdehydes, representing a further example of a carbonyl umpolung. F.e. (inch ring opening of satd. 4-, 5-, and 6-membered cyclic ethers) s. J.-M. Fang, M.-Y. Chen, Tetrahedron Letters 29, 5939 0 (1988) with oxo compds. cf. ibid. 5937-8. 

P-alkoxy-a,p-ethylenealdehydes 2-alkylidene-1,3-dialdehydes a,p-ethylene-5-hydroxyaldehydes a-methylenealdehydes... 

Z)-Hexanal oxime in THF treated dropwise under intensive stirring with 1.5 M BuLi soln. at 0°, stirred at room temp, for 20 30 min, recooled to 0°, a soln. of 2-pentanone in THF added dropwise, the mixture allowed to warm to room temp., and stirred for 4 h (Z)-2-butyl-3-methyl-3-hydroxyhexanal oxime. Y 99%. F.e. inch addition to a,p-ethylenealdehydes s. A. Hassner, F. Naumann, Chem. Ber. 121, 1823-6 (1988). 

P-Arylthio-a,P-ethylenealdehydes a-Arylthio-a,P-ethyleneketones 3-Hydroxythioenolethers 3-Hydroxy-2-thioenolethers 3-Ketothioenolethers P-Mercapto-a,p-ethyleneketones Thioenolesters Acylthioenols 10... 

Pyridine hydrobromide perbromide a,p-Ethylenealdehydes from salts of glycidic acids... 

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