Tris orthoformate

Some weak electrophilic reagents, which are usually inert toward azoles, also react with quaternized azoles. Diazonium salts yield phenylhydrazones (Scheme 48) in a reaction analogous to the Japp-Klingemann transformation of /S-keto esters into phenylhydrazones in the dithiolylium series illustrated the product has bicyclic character. Cyanine dye preparations fall under this heading (see also Section 4.02.1.6.5). Monomethine cyanines are formed by reaction with an iodo quaternary salt, e.g. Scheme 49. Tri- and penta-methinecar-bocyanines (384 n = 1 and 2, respectively) are obtained by the reaction of two molecules of a quaternary salt with one molecule of ethyl orthoformate (384 n = 1) or/S-ethoxyacrolein acetal (384 n =2), respectively. 

The mixed ortho ester formed from tri(2-chloroethyl) orthoformate (100°, 10 min-2 h, 16% yield) is more stable to acid than is the unsubstituted derivative, but can be cleaved with 80% AcOH (20°, 1 h). ... 

Triethyl orthoformate Orthoformic acid, triethyl ester (8) Ethane, l,l, l"-[methylidynetris(oxy)]tris- (9) (122-51-0)... 

Tris(phenylthio)methyllithium, (QHsS)3CLi (1). Tris(phenylthio)methane is prepared from thiophenol and trimethyl orthoformate. 

Both tris(2,2,2-trinitroethyl)orthoformate and tetrakis(2,2,2-trinitroethyl)-orthocar-bonate form powerfully explosive solutions in nitromethane. The oxygen balance of the esters are +154 and +182%, respectively. The compounds are Tetrakis(2,2,2-trinitroethyl)orthocarbonate, 3132 Tris(2,2,2-trinitroethyl) orthoformate, 2786 See OXYGEN BALANCE, POLYNITROALKYL COMPOUNDS... 

Orthoesters of polynitroaliphatic alcohols have been synthesized in the presence of metal chloride Lewis acid catalysts. Tetrakis(2,2,2-trinitroethyl)orthocarbonate (180) and tris(2,2,2-trinitroethyl)orthoformate (181) are obtained from the reaction of 2,2,2-trinitroethanol (159) with carbon tetrachloride and chloroform, respectively, in the presence of anhydrous ferric chloride.333729 Analogous reactions with 2-fluoro-2,2-dinitroethanol have been reported.3 ... 

Reaction of the quaternized salts of 4-ethoxycarbonyl-3,5-dimethyl-f-phenylpyttolo(furo or thieno)[2,3-c]pyrazole 34 with the iodomethane quaternary salts of pyridine, quinoline, and isoquinoline in ethanol with catalytic piperidine gave 3-[4(f)]-monomethine cyanine dyes (e.g., 35). Additionally, 3-[2(4)]-trimethine cyanine dyes and 4-[2(4)]-di-3[2(4)]-tri-mixed methine cyanine dyes (e.g., 36 and 37, respectively) were similarly prepared from the intermediates derived by reaction of 34 with triethyl orthoformate in the presence of piperidine (Scheme 8) <2002CCS106f>. 

Cyclization of 5-methoxy(nitro)-4-hydrazinopyrimidines (485) with tri-ethyl orthoformate gave the l,2,4-triazolo[4,3-c]pyrimidine intermediate 486, which cannot be isolated due to its conversion to its [1,5-c] isomer 487 by a Dimroth rearrangement. However, the 5-benzyloxypyrimidine derivative, under the same conditions, afforded a mixture of the 8-benzyloxy derivatives of both [4,3-c] and [l,5-c]isomers 486 and 487, respectively (86TL3127 89JHC687 90H277) (Scheme 95). 

All of these examples illustrate the complexing ability of an ax-eq-ax sequence of oxygen atoms on a six-membered or of a cis-cis sequence on a five-membered ring. Attempts have been made to find other complexing sites on sugar molecules but with little success. The 0-3, 0-5, and 0-6 arrangement of hexofuranoses, which allows the ready formation of tri-dentate periodate (IS), and orthoformate esters (19), does not form stable complexes with metal ions. In solution the side-chain of 1,2-0-isopropylidene-a-D-glucofuranose (13) is in the extended zig-zag form... 

The hydroformylation of styrene in triethyl orthoformate is slower than that observed in benzene, but a 98% ee is obtained, since racemization of the product acetal does not occur. Hydrolysis of the acetal to the aldehyde can be accomplished without racemization. A number of other substrates are hydroformylated in the presence of triethyl orthoformate. The reactions are slower, but with all substrates tried except norbomene, enantiomerically pure products can be obtained. 

ALKENES 1,3-Dimethyl-2-phenyl-l, 3,2-diazaphospholidine Iodine. Phenylthio(triphenylstannyl)methyllithium. Sodium amalgam. Sodium sulfide. Tri-n-butyltin hydride. Triethyl orthoformate. 

Refluxing compound 24 with triethyl orthoformate afforded the [ 1,2,4 ]tri-azolo[l,5-c]pyrimidine 25a, while with acetyl chloride or chloroacetyl chlo-... 

Dialkoxymethyllithiums 43 3649 and 434649 651, 2-lithio-l,3-dioxolane 435649 and 2-lithio-1,3-dioxane 436649 are formyl anion equivalents, which have been prepared either by reductive lithiation of 2-(phenylsulfanyl) substituted precursors at —95 °C649 or by trans-metallation of 2-(tri-n-butylstannyl) substituted compounds at —110649 or —78°C651. The starting acyclic phenylsulfanyl precursors can be prepared from the corresponding orthoformates by reaction with (phenylsulfanyl)trimethylsilane and trimethylsilyl triflate as catalyst (for compounds 433 and 434). The cyclic derivatives (435, 436) were prepared from l,2-bis(l,3-dioxolan-2-yloxy)ethane and propane, in the same way649. 

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