Acyl derivatives vinyl ethers

Formation of vinylic (trigonal C-Li), allylic or benzylic organolithiums a to O is more favourable. The useful acyl anion equivalent methoxyvinyllithium 11, for example, is formed on treatment of methyl vinyl ether with f-BuLi at -65 °C,13 and furan is lithiated by BuLi in Et20 at 0 °C to give 12.14 More complex carbohydrate-derived vinyl ethers such as 13 also lithiate readily.15... 

Recently Lin and coworkers have developed a selective synthesis of N-acyl and 0-acyl propanolol vinyl derivatives by enzyme-catalyzed acylation of propanolol using divinyl dicarboxylates with different carbon chain lengths (Scheme 7.10) [24]. Lipase AY30 in diisopropyl ether demonstrated high chemoselectivity toward the amino... 

Pyran-4-ones are formed when acyl ketenes derived from dioxofurans and dioxinones react with vinyl ethers. Intermediate products are 1,3,5-triketones and reduced pyranones <96CPB956,96H(43)2457,96TL6499>. 

The procedure described here offers a general route to a variety of unsymmetrically substituted y-pyrones from Meldrum s acid.2 Substitution at the 2-position depends on the acid chloride chosen, while substitution at the 5-position is derived from the vinyl ether. A variety of substituted y-pyrones have been synthesized by utilization of this method as illustrated in the Table. The intermediate pyrandione is believed to arise through the addition of the vinyl ether to an acyl ketene that results... 

Treatment of some iron-acyl complexes with trifluoromethanesul-phonic anhydride (TfzO) affords vinylidene derivatives directly (5 7,38). The reaction is envisaged as a nucleophilic attack on TfzO by the acyl, followed by deprotonation to the vinyl ether complex. A combination of an excellent leaving group (TfO-) with a good electron-releasing substituent on the same carbon atom facilitates the subsequent formation of the vinylidene ... 

Enantioselective Claisen rearrangement of allyl (a-trimethylsilyl)vinyl ethers in the presence of aluminium binaphthol derivatives gives ft-chiral y, <5-unsaturated acyl silanes with good ee (Scheme 33)114. 

An alternative was used by Baldwin in the work that led to his famous rules for cyclisation.8 He needed to study the cyclisation of the hydroxy-enone 36 and an obvious aldol disconnection led back to the a-hydroxy-ketone 37. The same disconnection requires the addition of an acyl anion equivalent 39 to cyclohexanone and Baldwin chose the lithium derivative 40 of a vinyl ether. 

Generally, treatment with electron-deficient olefins such as nitroethylene or vinyl sulfone is effective for radical addition reactions, since alkyl radicals derived from O-acyl esters (2) are nucleophilic and take SOMO-LUMO interaction. However, treatment of O-acyl esters ) derived from perfluoroalkyl carboxylic acids (RfC02H) generates electrophilic radicals, Rf, which react preferably with electron-rich olefins such as vinyl ether, as shown in eq. 8.16 [52]. 

Acid-catalyzed addition of aliphatic, aromatic or heteroaromatic cyanohydrins to ethyl vinyl ether, n-butyl vinyl ether or dihydro-4//-pyran provides base stable, protected cyanohydrin derivatives. Phase transfer catalyzed alkylation of aliphatic cyanohydrins with allylic bromides gave a-substituted a-allyl-oxyacetonitrile. Carbonyl compounds react wiA cyanide under phase transfer catalysis to give cyanohydrin anions, which are trapped by an acyl chloride or ethyl chloroformate to give acyl- or alkoxycarbonyl-protected cyanohydrins respectively. The reduction of the carbonyl group of an acyl cyanide by NaBH4 under phase transfer conditions followed by esterification serves as an alternative route to aldehyde-derived cyanohydrin esters. ... 

Amino nitriles are useful for conjugate addition Acyl anion equivalents of the ester d1 synthon - C02R Methods Based on Vinyl (Enol) Ethers and Enamines Lithium derivatives of cyclic vinyl ethers The synthesis of pederin and related anti-tumour agents Lithium derivatives ofallenyl ethers Oxidative Cleavage of Allenes... 

Acylation of sulfide and ether nucleophiles by protonated acyl derivatives is uncommon in condensed phase but, in the gas phase, ions of composition Ac+XMe2 are readily formed. For example, vinyl and iso-propenyl acetates acylate ethers under ICR conditions (11) ... 

BenzolMfurans yielded (2 + 2)-cycloadducts (191) with dimethyl-maleic anhydride, via excitation of an initially formed charge-transfer complex, together with oxetans.218 Similar (2 + 2)-cycloadducts (192) were obtained from quinones and benzoU>] furan and some of its derivatives.143,200 Irradiation of W-acyl-l//-indoles in the presence of olefins, either with or without acetophenone as a sensitizer, produced a series of (2 + 2)-cycloadducts 193, usually as a mixture of exo- and endoisomers.219 The olefins that give a (2 + 2)-cycloadduct are either electron-rich olefms, such as ethyl vinyl ether and vinyl acetate, or... 

Vinyl Ethers. a-Staimylated enol ethers provide a general and convenient substrate for introduction of acyl groups into azines (Scheme 94). The stannanes are available from enol ethers by a-lithiation and quenching with trialkylstannyl chloride. Mild acid hydrolysis of the a-pyrimidinylethenyl ethers yields the acyl-substituted pyrimidines such as the methyl pyrimidinyl ketone 259. The masked acyl group is introduced into the electrophilic 4-position in the 4,5-dichloro derivative 258. In 5-bromo-2-chloropy-rimidine, chemoselectivity leads to a masked acyl group in the 5-position 260. When the... 

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