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Prolonged reaction of 2,3,6-trimethoxytoluene with an excess of premixed (E)-2-methylbut-2-enoic acid and trifluoroacetic anhydride in air affords 5,6,8-trimethoxy-3,4,7-trimethylisocoumarin 11 in 66% yield as the sole product isolated, the structure of which was confirmed by X-ray crystallography. Shorter reaction times afford products which enable the identification of the reaction mechanism. This involves initial regioselective acylation, cyclisation of the derived α,β-unsaturated aryl ketone 5 to the cis/trans mixture of indanones 18 and 19 and O-acylation of these indanones to yield the indenyl ester 17. The indanones and compound 17 can all react with trifluoroacetic acid in the presence of atmospheric oxygen to afford the isocoumarin by a mechanism which requires the intermediacy of an α-keto indanyl hydroperoxide, which in turn undergoes an acid-catalysed Baeyer–Villiger-type rearrangement to incorporate oxygen, thereby giving the isocoumarin.

The enolate anions of 5-norbornen-2-one and 2-norbornanone enter into self-coupling with their conjugate acids in a manner that exhibits diastereomeric discrimination. The major products obtained from aldol reactions conducted at low temperature are those where bonding has occurred preferentially to the ketone of like absolute configuration. When the reactions are effected at higher temperatures, dehydration also occurs spontaneously. All indicators point to adherence by these bicyclic systems to molecular recognition in these condensation reactions as well. The aldol products, which are stable to the conditions under which they are formed, have been evaluated for their inherent levels of total energy and strain energy by molecular mechanics methods

The unique preparation of 2-substituted 4,7-dihydroxycyclohepta-3,5,7-triene-1,3-dicarboxylates 5 from aldehydes 4 and two equivalents alkyl 3-oxo-4-(triphenylarsoranylidene)butanoate 3 is described.

Alkyl 4-bromo- and 4-chloro-3-oxobutanoates were protected as silyl enol ethers. The Arbnzov reaction of these new compounds with triethyl phosphite gave the corresponding silyl enol phosphonates in high yield. Facile deprotection of the silyl group with water gave alkyl 4-(diethoxyphosphinyl)-3-oxobutanoates in high yields. Protection of 1-methylethyl 4-bromo-3-oxobutanoate as the enol acetate followed by the subsequent reaction with triethyl phosphite gave the corresponding phosphonate in high yield. Deprotection with potassium 2-propoxide gave 1-methylethyl 4-(diethoxyphosphinyl)-3-oxobutanoate in good yield. ©1997 John Wiley & Sons, Inc.

Methylation of α,β,γ,δ-unsaturated-β-substituted enol phosphates with lithium dimethyl cuprate gave a mixture of (2E,4E)- and (2Z,4E) alkyl 3-methylalka-2,4-dienoates and unsubstituted alkyl alka-2,4-dienoates. An improved synthesis is described for ethyl β-safranate and the insect growth regulator hydroprene.

A series of new substituted bis(benzoyl) peroxides has been synthesised from their corresponding acid chlorides in high yield. The reactions were carried out in aqueous sodium peroxide solution and butanone in the presence of 0.5% stearyltrimethylammonium chloride (STAC) at a temperature below 15°C. STAC improved the purity, and the fast addition improved the yield of the peroxides. Mass spectral analysis of substituted bis(benzoyl) peroxides using EI has been carried out for accurate mass determinations.

Separation of a mixture β-ketophosphonate 3 and their corresponding enol phosphate 4 is efficiently carried out in aqueous alkaline solutions. Enol phosphate 4 is first extracted with hexanes:dichloromethane (19:1). Acidification of the aqueous layer followed by extraction of the β-ketophosphonate 3 with dichloromethane completes the separation. Thus, when 1-bromo-2,4-pentadione 1a reacted with triethyl phosphite to give diethyl (2,4-dioxopentyl)phosphonate 3a (Arbuzov-product) and the corresponding enol phosphate 4a (Perkow-product), separation of the two compounds was carried out using this method.

2,4-Dioxopentyltriphenylphosphonium bromide reacted with aqueous sodium hydrogencarbonate in dichloromethane to give, in almost quantitative yield, 1-(triphenylphosphoranylidene) pentane-2,4-dione. Dianion Wittig- and Michael Wittig condensations of the last mentioned phosphonium ylide with carbonyl compounds gave unsaturated 2,4-diketones which were almost totally enolised in deutero chloroform as 4-hydroxy-2-oxo-3,5-dienes (24–70% yields). These products closely resembled the type of compounds derived from similar condensations with alkyl 3-oxo-4-(triphenylphosphoranylidene)butanoate.

The 4-phosphinyl-3-oxobutanoates (II) are transformed into the dianions (I) or into the monoanions (IV) and (V), depending on the type and amount of bases used.