Alkyl chloroformates, alkylation with

The alkyl chloroformates react with cold ethereal dispersions of the xanthates to give the fairly stable xanthogen formates. 

The reaction of arylisothiocyanates with guanidines (233) affords amidinothioureas (234), which can be converted into 3,5-diarylimino-l,2,4-thiadiazolines (235) directly on treatment with bromine in ethanol. Alternatively, (234) can be alkylated with benzyl chloride to give the S-benzyl derivative (236) which on treatment with bromine in chloroform gives (235) (Scheme 51) <87JIC675>. 

Tetrazolyl)-4//-pyrido[l,2-a]pyrimidin-4-ones 441 were alkylated with alkyl iodides, alkyl bromides, triethyl phosphate, cyclopentyl bromide, allyl bromide, propargyl bromide, benzyl chlorides, ethyl bromoace-tate, and methyl chloroformate in dimethylformamide in the presence of potassium carbonate at 80-90°C to give a mixture of 3-(l-substituted 5-tetrazolyl)- and 3-(2-substituted 5-tetrazolyl)-4//-pyrido[l,2-u]pyrimidin-... 

The mercapto group of 9-mercapto-4//-pyrido[ 1,2-a]pyrimidin-4-ones 513 was alkylated with (het)aralkyl bromides and chlorides in the presence of potassium carbonate in dimethylformamide at ambient temperature for several hours. It also was acylated with carboxyl chlorides in the presence of potassium carbonate in acetone at room temperature or with mixed anhydride, prepared from aryl carboxylic acid and ethyl chloroformate,... 

Nitrosation at the 5-position of 3-methoxy-4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridine (237) has been used as a method to block this basic nitrogen in the synthesis of compound (242) (Scheme 23), a conformationally restricted 7V-methyl-(/ )-aspartic acid analogue, for evaluation as a potential excitor of neurotransmitters in the mammalian central nervous system <82Mi 708-02, 86ACS(B)92>. Lithiation of the derivative (238) with n-butyllithium regiospecifically at the 4-position followed by C-alkylation with the addition of methyl chloroformate gave the 4-methoxycarbonyl derivative (239), albeit in a low 16% yield. The remainder of the synthetic sequence involves a stepwise deprotection sequence (239)-(242). 

Krief et al. have shown that selenium ylides behave as their sulfur analogues and convert a variety of carbonyl compounds to oxiranes <89H(28)1203>. The latter compounds can be directly obtained by using R2Se=CHR /i-hydroxyalkylselenides (available from carbonyl compounds by addition of RSeCH2Li) may serve as suitable precursors as well, either in a two-step protocol, via the selenonium salt by alkylation with magic methyl (MeS03F), or directly by treatment with thallous ethoxide in chloroform. Oxidation of the /t-hydroxyalkylselenides with peracid, followed by treatment of the resulting selenone with base, results in oxirane formation (Scheme 60). 

Least et al. reduced the sample size to 20 pi serum, plasma, or saliva, in a microscale procedure. The extraction was carried out with a chloroform-isopropanol solution of the internal standard, 3-isobutyl-l-methylxanthine. After alkylation with tetramethylammonium hydroxide and pentyl iodide, gas chromatography was carried out on a packed 3 OV-17 on Gas Chrom Q column, by temperature programming from 180°C to 260°C, and using a nitrogen sensitive detector. With the sample volume used, the background interference is equivalent to about 0.1 mg/litre, and 0.5 mg theophylline per litre can easily be measured. Between-run... 

The reaction of silylated fluoromethylphosphonate carbanions with a large variety of alkyl, vinyl, or aryl chloroformates or with carbon dioxide proceeds smoothly at low temperature to give silylated l-(alkoxycarbonyl)-l-fluoromethylphosphonates and 1-(hydroxycarbonyl)-1-fluoromethylphosphonate, respectively (Scheme 3.58). For the electron-withdrawing carboxyl group, the traces of base already present in the reaction medium are sufficient to effect a desilylation if EtOH is added to the mixture. The desilylated products are isolated in 80-91% yields." - " The addition of EtOLi leads to decomposition with loss of phosphate. 

Acylation of dialkyl cyanomethylphosphonates was first accomplished using potassium metal in Et2O and acyl chlorides. The resulting a-cyano-3-kctoalkyIphosphonates were isolated in modest yields (24-36%), usually as a mixture of the keto and enol forms. The recently reported procedure using powdered NaOH or KOH in MeCN offers a more convenient route and better yields (17-90%, Scheme 6.14). 2-Chloroethyl chloroformate reacts with sodium diethyl cyanomethylphosphonate in THF to produce diethyl l-cyano-(l,3-dioxolan-2-ylidene)methylphosphonate in 83% yield by a C-acylation-O-alkylation sequence. 

The 209D diastereomer (+ )-590 has also been made by Comins and Zhang (Scheme 78) 466,467). After 77-acylation of the 4-methoxypyridine 591 with (1 S,2R,4S)-4-isopropyl-2-( 1 -methyl-1 -phenylethyl)cyclohexyl chloroformate, the resulting pyridinium salt was intercepted with hexylmagnesium chloride to give the optically active enaminone 592. Removal of the chiral auxiliary and A -alkylation with (Z)-l,3-diiodopropene yielded 593, thereby setting the scene for a novel anionic... 

The selective alkylation with alkyl halides of 2,1,3-benzothiadiazinones 1 at oxygen leads to the benzothiadiazinium salts 2. The starting compounds 1 are, in analogy to 2,1,3-benzothiadiazin-4(3//)-ones that are unsubstituted on the benzene ring,133 accessible from 2-aminobenzimi-damides by reaction with V,Ar-ditosylsulfur diimides in chloroform.134 The reaction of 1 with oxonium salts in dichloromethane also gives the 2,1,3-benzothiadiazinium salts 2.134... 

Many other nucleophilic reactions of peroxides are known, and some of the products have found use as polsnmerization catalysts. The peroxide group can be alkylated with halides (9), sulfates (10), and sulfonates (11), and reaction with an epoxide gives a -hydroxyalkyl peroxide (12). Nucleophilic attack at the carbonyl group of acid chlorides (13), carbonyl chloride, chloroformates (H), acid anhydrides (3), ketenes (15), and iso-... 

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