1.1.2- tris ethoxycarbonyl

A one-step synthesis of pyrazolo[3,4-inverse electron demand cycloaddition of2,4,6-tris(ethoxycarbonyl)-l,3,5-triazineand5-aminopyrazoles involving loss... 

The reaction of 8-chlorotheophyllines with nitrilium imides to give [l,2,4]triazolo[3,4y]purines may be described as a [3+2] cycloaddition process <2001JOC4055> see Section 10.11.5.1. The purine bicycle has been prepared through the Diels-Alder-retro-Diels-Alder reaction of 2,4,6-tris(ethoxycarbonyl)-l,3,5-triazine with 5-amino-l-benzylimida-zole <1999JA5833> see Section 10.11.10.3. 

The well-known application of 2,4,6-tris(ethoxycarbonyl)-l,3,5-triazine as a diene in inverse electron demand Diels-Alder cyclizations was adapted for the synthesis of purines <1999JA5833>. The unstable, electron-rich dienophile 5-amino-l-benzylimidazole was generated in situ by decarboxylation of 5-amino-l-benzyl-4-imidazolecarboxylic acid under mildly acidic conditions (Scheme 54). Collapse of the Diels-Alder adduct by retro-Diels-Alder reaction and elimination of ethyl cyanoformate, followed by aromatization by loss of ammonia, led to the purine products. The reactions proceeded at room temperature if left for sufficient periods (e.g., 25 °C, 7 days, 50% yield) but were generally more efficient at higher temperatures (80-100 °C, 2-24 h). The inverse electron demand Diels-Alder cyclization of unsubstituted 1,3,5-triazine was also successful. This synthesis had the advantage of constructing the simple purine heterocycle directly in the presence of both protected and unprotected furanose substituents (also see Volume 8). 

The presence or absence of the dioxolane protecting group in dienes dictates whether they participate in normal or inverse-electron-demand Diels-Alder reactions.257 The intramolecular inverse-electron-demand Diels-Alder cycloaddition of 1,2,4-triazines tethered with imidazoles produce tetrahydro-l,5-naphthyridines following the loss of N2 and CH3CN.258 The inverse-electron-demand Diels-Alder reaction of 4,6-dinitrobenzofuroxan (137) with ethyl vinyl ether yields two diastereoisomeric dihydrooxazine /V-oxide adducts (138) and (139) together with a bis(dihydrooxazine A -oxide) product (140) in die presence of excess ethyl vinyl ether (Scheme 52).259 The inverse-electron-demand Diels-Alder reaction of 2,4,6-tris(ethoxycarbonyl)-l,3,5-triazine with 5-aminopyrazoles provides a one-step synthesis of pyrazolo[3,4-djpyrimidines.260 The intermolecular inverse-electron-demand Diels-Alder reactions of trialkyl l,2,4-triazine-4,5,6-tricarboxylates with protected 2-aminoimidazole produced li/-imidazo[4,5-c]pyridines and die rearranged 3//-pyrido[3,2-[Pg.460]

Auf analoge Weise ist Phosphorsdure-tris-[ethoxycarbonyl-amid] (75%) aus Phosphor-saure-tris-[isocyanat] mit Ethanol (in Acetonitril, 5-10°) zuganglich948. 

Aminopyrazoles react as dienophiles in inverse electron demand DielsAlder reactions of 2,4,6-tris(ethoxycarbonyl)-1,3,5-triazine in a synthesis of pyrazolo[3,4- ]pyrimidines <1996JOG5204>. 

Reaction of 5-amino-l -benzyl-4-imidazolecarboxylic acid 495 with 2,4,6-tris(ethoxycarbonyl)-1,3,5-triazine 496 at 80 °C in DMF led to 9-benzyl-2,6-bis(ethoxycarbonyl)purine 501 in 83% yield. Presumably, 5-amino-l-benzyM-imidazole 497 is generated siVu from the acid and is highly reactive for the cycloaddition. The cycloadduct 498 then spontaneously undergoes retro Diels-Alder reaction with the loss of ethyl cyanoformate 499 followed by the loss of ammonia and aromatization to produce the purine in a regioselective manner (Scheme 114) <1999JA5833, 2005JOC998>. 

Tris(ethoxycarbonyl)-l,3,5-triazine reacts with ynamines and enamines in [4- -2] cycloadditions followed by a retro-Diels-Alder reaction 2,4,6-tris-(methylthio)-l,3,5-triazine reacts only with ynamines (Scheme 14) <88T3379>. 

Addition of electron-withdrawing substituents, as in 2,4,6-tris(ethoxycarbonyl)-l,3,5-triazine, increases the rate of participation in Diels-Alder reactions. 2,4,6-Tris(ethoxycarbonyl)-... 

Tris(ethoxycarbonyl)-l,3,5-triazine serves as an azadiene in reaction with 5-aminopyrazoles to produce purine isosteres, pyrazolo[3,4-t ]pyriniidines." In order to overcome the relative instability of 5-aminoiniidazoles, required for analogous synthesis of purines, 5-aminoiniidazole-4-carboxylic acids can be used, in situ decarboxylation producing the required dienophile."" ... 

Thermal reaction of the amidine 91 with 2,4,6-tris(ethoxycarbonyl)-l,3,5-triazine 87 provided only low conversion to the desired pyrimidine 92 and these results contrasted the effective conversion (75%) observed with the unsubstituted 2-iminopiperidine hydrochloride itself (Equation 10) <1998BMC643>. 

Tris(ethoxycarbonyl)methyl methoxycarbonyl nitroxide (C2H502C)3C—IJJCO2CH3 o- Thermally activated reaction of (C03C(CH3)3)2 + HCO2CH3 + (C2H502C)3CN0/ CeHs EPR/ 288 N 0.773 3H 0.041 75Flel... 

Preparation by reaction of boron tribromide with 2,2, 3 -tris[(ethoxycarbonyl)oxy]-6-methoxybenzo-phenone (SM) in methylene chloride at r.t. for 5 h under nitrogen (61%) [412]. SM was obtained by... 

The ethoxycarbonyl group was developed for the protection of phosphonates. The derivative is prepared by reaction of tris(trimethylsilyl) phosphite with ethyl chloroformate and can be cleaved by hydrolysis of the ester followed by silyla-tion with bistrimethylsilylacetamide. ... 

Experimental Procedure 3.1.4. Preparation of a Molybdenum Vinylidene Complex from a Carbyne Complex Tetrabutylanunoniuih Cyano(ethoxycarbonyl) vinylidene (dicarbonyl) hydro-tris(3,5-dimethyl-1 -pyrazblyl)borato molybdenum [526] [37] pp 151 and 188... 

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>. 

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