Methoxymethyl vinyl ketone

Cycloadditions.1 Acyclic enones do not usually undergo photochemical l2+2]cycloaddition with alkenes, but this Ti(lV) Lewis acid does promote this cycloaddition in the case of methoxymethyl vinyl ketone and, to a less extent, of methyl vinyl ketone. Usually 2 equiv. of 1 or of TiCl2(0-/-Pr)2 is required. 

Section 1.1.2.1.2 (ii) a,0-Unsaturated ketones and aldehydes. Engler and coworkers found that a 1 1 mixture of TiCU and Ti(OPr )4 catalyzes the addition of methoxymethyl vinyl ketone to styrenes and methylenecyclohexane to give cyclobutanes. 

Preparation. Wenkert and Berges1 generated the reagent in situ from 1,4-dimethoxy-2-butanone2 by reaction with ethanolic potassium hydroxide. Ireland et al.3 prepared the reagent in crude form by the pyrolysis of 1,4-dimethoxy-2-butanone with sodium benzoate.4 In a typical reaction 10.06g. of the precursor on pyrolysis with 12.5 g. of sodium benzoate afforded 4.38 g. of distillate that contained 2.7-2,8g. of methoxymethyl vinyl ketone (assayed by vpc and NMR). This crude distillate can be used directly for annelation.5... 

Methoxymethylsulfonate, 198 Methoxymethyl vinyl ketone, 198-199 7-Methoxynorcarane, 103 2 -Methoxytetrahydxopyranyladenosine, 198 5 -O -Methoxytetrahydropyranylthymidine, 198... 

ANNELATION 0-Chloroethyl vinyl ketone. l-Chloro-3-pentanone. Methoxymethyl vinyl ketone. fwis-3-Pentene-2-one. 

Methoxymethyl vinyl ketone undergoes titanium(lV) chloride/titanium tetraisopropoxide catalyzed cycloaddition to either stereoisomer of 1-phenylpropene to give a mixture of the two cyclobutanes which could be equilibrated to the rrans.rrans-isomer with carbonate42. 

Startg. p-methylstyrene added to a soln. of methoxymethyl vinyl ketone and 1 eq. 1 1 TiCl4/Ti(OPr-/)4 in dichloromethane at —78°, warmed to —20°, 1 N HCl added, worked up, and the epimeric acylcyclobutanes treated with methanolic K2CO3 product. Y 58-89%. Reaction with unactivated alkenes is facilitated by the a-me-thoxy group which coordinates to the metal in the intermediate Ti(IV)-enone complex. F.e.s. T.A. Engler et al.. Tetrahedron Letters 30, 1761-4 (1989). 

DIALKYLACETIC ACIDS 2-Methyl-4-methoxymethyl-5-phenyl-2-oxazoline. frans-2,3-DlALKYLCYCLOPENTANONES Lithium methyl(vinyl) cuprate. a, a-DIALKYL KETONES Diphenyl disulfide. 

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