Cornelis M. Moorhoff

Novel reactions of arsonium ylides and substituted 2H-pyran-5-carboxylates, a new preparation for functionalised vinylcyclopropanecarboxylates and dihydrofurans

Substituted alkyl 2-pyran-5-carboxylates have been condensed with arsonium ylides to form substituted vinylcyclopropanecarboxylates and in a number of cases also vinyldihydrofurans.

Novel Michael-Wittig reactions of methyl 3-oxo-4-(triphenylarsoranylidene)butanoate and substituted 2H-pyran-5-carboxylates; The synthesis of highly functionalised 2-cyclohexenonedicarboxylates

Novel Michael-Wittig condensations of methyl 3-oxo-4-(triphenylarsoranylidene)-butanoate 6 and substituted 2,2-dimethyl-2H-pyran-5-carboxylates 5a to 5e gave substituted 4-alkyl-6-oxo-4-cyclohexene-1,3-dicarboxylates 8a to 8e in a mixture of three keto diastereomers and two enol diastereomers. Apart from substituted 4-alkyl-6-oxo-4-cyclohexene-1,3-dicarboxylates 8f to 8g, less hindered substituted 2-methyl-2H-pyran-5-carboxylates 5f and 5g gave the substituted tetrahydrobenzofurans 9f and 9g. 4-Halomethyl-6-oxo-4-cyclohexene-1,3-dicarboxylates 8 were mostly in the enol diastereomeric form. A plausible mechanism is given for the unique formation for these products.

A General Method for the Rapid High Yield Preparation of Pure Arsonium Salts. Preparation Of (3-Alkoxy-Carbonyl-2-Oxopropyl)Triphenylarsonium Bromides

Abstract An easy, rapid method for the preparation of arsonium salts of high yield and purity, by heating an alkyl halide and triphenylarsine as a melt at about 80°C, is described.

Sodium Benzoate as a Mild Base Catalyst for the Tandem Michael-Aldol Self-Condensation of γδ-Unsaturated β-Ketoesters

Summary. An efficient procedure has been developed for the tandem Michael-aldol self-condensation of δ,γ-unsaturated β-ketoesters (1), using sodium benzoate as a mild base catalyst to furnish conjugated vinylcyclohexenonedicarboxylates (2) some of which show biological activity against ectoparasites in cattle.Zusammenfassung. Natriumbenzoat ist als milder basischer Katalysator ausgezeichnet zur Anwendung bei der Tandem-Michael-Aldol-Selbstkondensation von γ,δ-ungesättigten β-Ketoestern (1) geeignet. Es entstehen Vinylcyclohexenondicarboxylate (2), von denen einige biologische Aktivität gegen Ektoparasiten bei Rindern zeigen.

An unusual condensation of alkyl 3-oxo-4-(triphenylarsoranylidene)butanoate with aldehydes; synthesis of symmetrical substituted 1,3,5-cycloheptatrienes

Abstract 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.

Silyl enol ethers as protective groups for alkyl 4-halo-3-oxobutanoates in the Arbuzov reaction with triethyl phosphite

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.

Condensations of γ-acetylacetonephosphonium ylide (1-(triphenylphosphoranylidene) pentane-2,4-dione) with carbonyl compounds

Summary. 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.