Dicarbon

Indole (10mmol) was added to dry CH3CN (20 ml) and the mixture stirred while DMAP (122 mg, 1,00 mmol) and di-tert-butyl dicarbonate (2.62 g. 12 mmol) were added. Evolution of gas was noted and stirring was continued... 

Pyrocarbonates or dicarbonates (anhydrides of carbonic acids) have been prepared as follows (29) ... 

DI Wfi-BUTVL BICARBONATE [Dicarbonic acid, di- er -butyl ester]... 

B. Di-tert-butyl dicarbonate. A solution of 20.0 g. (0.076 mole) of di-i-butyl tricarbonate in 75 ml. of carbon tetrachloride is placed in a 600-ml. beaker fitted with a magnetic stirrer, and 0.10 g. (0.0009 mole) of freshly sublimed l,4-diazabicyclo[2.2.2]octane (DABCO) is added (Note 9). Rapid evolution of carbon dioxide begins at once. The reaction mixture is stirred at 25° for 45 minutes to complete the loss of carbon dioxide (Note 10), and then 35 ml. of water, containing sufficient citric acid to make the aqueous layer slightly acidic, is added. The layers are separated and the organic layer is dried over anhydrous magnesium sulfate and then concentrated at 25° with a rotary evaporator. The residual liquid is distilled under reduced pressure to separate 13.3-15.1 g. (80-91%) of di-butyl dicarbonate as a colorless liquid, b.p. 55-56° (0.15 mm.) or 62-65° (0.4 mm.) n T> 1.4071-1.4072 (Note 11). 

The submitters report that both l,4-diazabicyclo[2.2.2]octane and triethylamine have been used to catalyze this decomposition. Tri-ethylamine was less satisfactory as a catalyst because of its relatively rapid reaction with the solvent, carbon tetrachloride, to form triethylamine hydrochloride and because of difficulty encountered in separating triethylamine from the dicarbonate pi oduct. The 1,4-diazabicyclo-[2.2.2]octane was efficiently separated from the dicarbonate product by the procedure described in which the crude product was washed with very dilute aqueous acid. 

A number of less-hazardous reagents that can be substituted for tert-hutyl azidoformate in tert-butoxycarbonylation reactions are available including 2-(te/t-butoxycarbonyloxyimino)-2-phenylacetonitrile (Aldrich Chemical Company), 0-teri-hutyl N-phenyl thiocarbonate (Eastman Organic Chemicals), di-butyl dicarbonate and tert-butyl phenyl carbonate. ... 

The functionalized allene, DIMETHYL 2,3-PENTADIENEDIOATE, the first in the series, is an intriguing substrate for various addition and cycloaddition reactions. Finally, a new reagent, DI-ferf-BUTYL DICARBONATE, for he formation of A-f-BOC derivatives which eliminates the use o the hazardous fert-BUTYL AZIDOFORMATE (WARNING) is intrqduced. 

Hydrazine azide Hydrazine chlorate Hydrazine dicarbonic acid diazide Hydrazine perchlorate Hydrazine selenate Hydrogen cyanide, unstabilized Hydroxyl amine iodide Hyponitrous acid... 

Many novel cluster compounds have now been prepared in this way, including mixed metal clusters. Further routes involve the oxidative fusion of dicarbon metallacarborane anions to give dimetal tetracarbon clusters such as (103) and (104) O (jjg insertion of isonitriles into inetallaborane clusters to give monocarbon meiallacarboranes such as (105) and the reaction of small ii/t/o-carboranes with alane adducts such as Et3NAlH3 to give the commo species (106) ... 

Consider the electronic ground state of dicarbon C2. Elementary arguments would suggest a ground state configuration... 

A) PivaloyloxymethylD(—j-Oi-azidobenzylpenicillinate Toa suspension ofpotassiumD(—)-a-azidobenzylpenicillinate (4.14g) and potassium dicarbonate (1.5 g) in acetone (100 ml) and 10% aqueous sodium iodide (2 ml), chloromethyl pivalate (2.7 ml) was added and the mixture refluxed for 2 hours. After cooling, the suspension was filtered and the filtrate evaporated to dryness in vacuo. The remaining residue was washed repeatedly by decantation with petroleum ether to remove unreacted chloromethyl pivalate. The oily residue was taken up in ethyl acetate (100 ml), and the resulting solution washed with aqueous sodium bicarbonate and water, dried and evaporated in vacuo to yield the desired compound as a yellowish gum, which crystallized from ether, melting point 114°C to 115°C. 

Amino groups are often protected as their tert-butoxycarbonvl amide, or Boc, derivatives. The Boc protecting group is introduced by reaction of the amino acid with di-fert-butyl dicarbonate in a nucleophilic acyl substitution reaction and is removed by brief treatment with a strong organic acid such as trifluoro-acetic acid, CF3C02H. 

Problem 26.16 Show the mechanism for formation of a Boc derivative by reaction of an amino acid with di-fe/t-butyl dicarbonate. 

Predict the product of the reaction of valine with the following reagents (a) CH3CH2OH, acid (b) Di-fert-butyl dicarbonate... 

I.3.3.2.2.I. Reagents Representing a,y-Dicarbon-Substituted Allyl Anions... 

Table 4. Utilization of 1,3-Dicarbon-Substituted Allyl Anions in Enantioselective Carbonyl Addition Reactions...

Di-tert-butyl dicarbonate and 4-dimethylaminopyridine were purchased from Alfa-Aesar Chemical Company and used without further purification. 

Triturating with diethyl ether was found to be necessary to successfully remove residual di-tert-butyl dicarbonate and di-tert-butyl iminodicarboxylate which may be produced as a result of residual traces of ammonia from step A. 

Natriumboranat/Aluminiumchlorid, Zinn(IV)-chlorid und Titan(IV)-chlorid reduzieren ebcnfalls Dicarbon-saure-imide wahrend Diboran auch bei groBem OberschuB und hohercn Temp, nur schlechte Ausbeuten liefert. 

A, A -dibutyl-2-bromoacetamide (C, H2oBrNO 40124-27-4) see Halofantrine di-tcrr-butyl dicarbonate see under bis( 1,1 -dimethylethyl) dicarbonate... 

Certain reagents promote ring opening and subsequent cyclization to give other heterocycles. For example, di-tert-butyl dicarbonate induces the stereoselective ring transformation of N-alkyl aziridines 159 into oxazolidin-2-ones 160 <96TET2097>. 

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