Sulfuric acid 137 Wittig reaction

Dimsylsodium (24) functions as a highly basic sulfur ylide. It can be used to convert phosphonium salts to phosphorus ylides for use in the Wittig reaction. Dimsylsodium also reacts with aldehydes and ketones by nucleophilic addition to form epoxides and with esters by nucleophilic substitution to yield p-ketosulfoxides (25) (Scheme 11). The p-ketosulfoxides (25) contain acidic a-hydrogens which can be readily removed to allow alkylation, and the products (26) suffer reductive desulfuration on treatment with aluminium amalgam to yield ketones (27) (Scheme 11) This procedure can, for instance, be applied to the conversion of ethyl benzoate to propiophenone (28) (Scheme 12). 

Dimethoxybenzaldehyde was prepared by Wittig as follows 210 When a mixture of resorcinol dimethyl ether (13.8 g, 0.1 mole) and phenyllithium (0.1 mole) in anhydrous ether (100 ml) is kept at room temperature for 60 h, the lithio derivative separates as large transparent crystals. Then A-methylformamide (13.5 g), dissolved in anhydrous ether (100 ml), is dropped in, which causes the mixture to boil. When the main reaction has ceased, the mixture is set aside for 0.5 h, then poured into an excess of dilute sulfuric acid. The ether layer is separated, dried, and freed from solvent. The residue is distilled at 13 mm until the vapor temperature reaches 130°. The residue in the distillation flask crystallizes from cyclohexane or much water in needles, m.p. 98-99°. The yield is 55%. 

The very first reported PHOST that is transparent in the DUV was prepared by thermolysis or acidolysis of PBOCST, which is in turn prepared via radical polymerization of the BOCST monomer by 2,2-azobis(butyronitrile) (AIBN), benzoyl peroxide (BPO), or other radical initiators. The BOCST monomer can be prepared by the Wittig reaction on a protected 4-hydroxybenzaldehyde with a rather high yield due to the good stability of the t-BOC group toward a base cata-lyst. " The PBOCST polymer thus obtained is readily converted to PHOST by heating the polymer to 200°C or by treating the polymer with an acid such as acetic acid or HCl in solution. And PBOCST can be synthesized via cationic polymerization in liquid sulfur dioxide. ... 

The (S)-lactone acid 1, obtained from L-glutamic acid by nitrous acid deamination, was converted to the acid chloride, then treated with excess diazomethane followed by hydrogen iodide to yield the keto-lactone 2. Amidation occurred quantitatively to give the partially racemized amide 3, which was purified by repeated recrystallizations. The vicinal diol resulting from reaction with excess methylmagnesium iodide was protected as the acetonide 4. An isomeric mixture of olefins (Z , 26 74) was obtained from the subsequent Wittig reaction. Reduction followed by separation on silver nitrate coated silica gel gave the (Z)-and ( )-alcohols in 20% (6) and 61% (5) yield, respectively. Conversion of the (S)-( )-alcohol (5) to the chloride then afforded the thioether (7) on reaction with sodium phenylsulfide. The thio ether anion was formed by treatment with n-butyllithium. Alkylation with the allylic chloride" (8), followed by removal of sulfur, then yielded the diene 9, which was converted in several steps to (/ ) (-t-)-10,11 -epoxy famesol. 

Ramazani, A., Abdian, B., Nasrabadi, F. Z., and Rouhani, M. (2013). The reaction of N-isocyaniminotriphenylphosphorane with biacetyl in the presence of ( )-cinnamic Acids Synthesis of fuUy substituted 1,3,4-oxadiazole derivatives via intramolecular aza-Wittig reactions of in situ generated iminophosphoranes. Phosphorus Sulfur Silicon Relat. Elem., 188, 642-648. 

Electrophilic substitution of the ring hydrogen atom in 1,3,4-oxadiazoles is uncommon. In contrast, several reactions of electrophiles with C-linked substituents of 1,3,4-oxadiazole have been reported. 2,5-Diaryl-l,3,4-oxadiazoles are bromi-nated and nitrated on aryl substituents. Oxidation of 2,5-ditolyl-l,3,4-oxadiazole afforded the corresponding dialdehydes or dicarboxylic acids. 2-Methyl-5-phenyl-l,3,4-oxadiazole treated with butyllithium and then with isoamyl nitrite yielded the oxime of 5-phenyl-l,3,4-oxadiazol-2-carbaldehyde. 2-Chloromethyl-5-phenyl-l,3,4-oxadiazole under the action of sulfur and methyl iodide followed by amines affords the respective thioamides. 2-Chloromethyl-5-methyl-l,3,4-oxadia-zole and triethyl phosphite gave a product, which underwent a Wittig reation with aromatic aldehydes to form alkenes. Alkyl l,3,4-oxadiazole-2-carboxylates undergo typical reactions with ammonia, amines, and hydrazines to afford amides or hydrazides. It has been shown that 5-amino-l,3,4-oxadiazole-2-carboxylic acids and their esters decarboxylate. 

A copper-catalyzed synthesis of benzo[f)]thiophenes and benzothiazoles using thiocarboxylic acids as sulfur source and coupling partner in the presence of Cul and 1,10-phenanthroline (1-10 phen) was developed this year (13JOC8898). The reaction proceeds by UUmann-type C—S bond coupling followed by Wittig condensation. 

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