Nitro acetates

Benzyl isocyanoacetate is a useful reagent for the preparation of benzyl 5-unsubstituted pyrrole-2-carboxylates, which are widely used in the synthesis of porphyrins.23 Ono and coworkers have prepared pyrroles substituted with various substituents at the (3-positions.231 Because the requisite (3-nitro acetates (or nitroalkenes) are readily available by the Henry... 

Total synthesis of phytochromobilin starting from 2-tosylpyrroles, which are prepared by (3-nitro acetates with TosMIC (Scheme 10.4) has been reported.28 Phytochrome is a chromoprotein concerned in a variety of processes in higher plants such as growth, development, and morphogenesis, 29... 

Reagent prepared by adding 4.5 g. of 70% nitric acid to 3S ml. of acetic anhydride at 25-30° reacts with simple alkenes to give mixtures of/3-nitro acetates, nitrooleflns,... 

Utilizing the Wittig-Horner reaction. The readily prepared /3-nitro-acetals (36) have been used as equivalents for /3-acylvinyl anions (CH=CHCOR). 1-Bromo-2-ethoxycyclopropyl-lithium is the synthetic equivalent of the 2-lithio-propenal moiety (Scheme 52). 4-Nitrobut-l-ene forms the dianion (37) which... 

Certain features of the addition of acetyl nitrate to olefins in acetic anhydride may be relevant to the mechanism of aromatic nitration by this reagent. The rapid reaction results in predominantly cw-addition to yield a mixture of the y -nitro-acetate and y5-nitro-nitrate. The reaction was facilitated by the addition of sulphuric acid, in which case the 3rield of / -nitro-nitrate was reduced, whereas the addition of sodium nitrate favoured the formation of this compound over that of the acetate. As already mentioned ( 5.3. i), a solution of nitric acid (c. i 6 mol 1 ) in acetic anhydride prepared at — 10 °C would yield 95-97 % of the nitric acid by precipitation with urea, whereas from a similar solution prepared at 20-25 °C and cooled rapidly to —10 °C only 30% of the acid could be recovered. The difference between these values was attributed to the formation of acetyl nitrate. A solution prepared at room... 

Treatment of fi-nitro acetates with thiols in the presence of base is also a simple method for the preparation of fi-nitro sulfides fEq. 4.3). 

C-Alkyldtkin takes place in the reaction of methyl nitroacetate with ilkyl h ilicles the products are useful intermediates for preparing amino acids fEq. 5.1 /The requisite nitro acetate is prepared by seif condensadon of nitromethane. ... 

Preparation of Memfield resin-bound nitro acetates, which is a suitable bndding block for the development of combinatorial solid phase synthesis, is repotted. The anion of ethyl nitro acetate is generated in DMF by an electrochemical method using Pt cathode, magnesium rod anode, and tetrabutylairunonium bromide as an electrolyte. Alkylaton of this anion with alkyl hahdes gives mono-alkylated products in 80% yield." ... 

Many other biologically active pyrroles have been prepared by this reaction. 3-Cyano-3,4-disubsdnited pyrroles are prepared by thereacdon ofisocyanoacetonitnie v/ithfi-nitro acetates. 

Bordwell and Garbisch71 contested this conclusion since they found that nitric acid in acetic anhydride prepared at —10 °C contained a much less effective nitrating species (the nitric acid could be recovered quantitatively) than when mixed at 25 °C and cooled to —10 °C (the nitric acid being then mostly unrecoverable). Further, these latter solutions reacted with alkenes to give predominantly cis addition products (nitro-acetates), whi h indicates association of the nitronium ion with some other species. It has been argued72 that this does not necessarily follow, since nitration of aromatics may involve a different... 

The palladium-catalyzed cross-coupling reaction featured in this procedure occurs under neutral conditions in the presence of many synthetically useful functional groups (e.g. alcohol, ester, nitro, acetal, ketone, and aldehyde). The reaction works best in N,N-dimethylformamide with bis(triphenylphosphine)palladium(ll) chloride, PdCI2(PPh3)2, as the catalyst. Lithium chloride is added to prevent decomposition of the catalyst.143 13 It is presumed that conversion of the intermediate aryl palladium triflate to an aryl palladium chloride is required for the transmetallation step to proceed.9... 

Ds Specification MIL-D-6998B (June 1967) MoncmitrodichloTomethane, CHCI2.NO2 mw 129-94, N 10.78% oil, bp 106-07° was prepd by passing Cl into an aq soln of K salt of nitro-acetic acid (O2N.CH2.COOK) (Refs 1 2) Refs 1) Beil 1, jll3i 2) W. Steinkopf ... 

This product was characterized by its NMR spectrum and also by reaction with HC1 followed by BF3/methanol to yield methylcyanoacetate ester. The reaction occurs readily, and in the absence of detectable amounts of the oxidative addition product of acetonitrile with the iridium complex, [Hlr-(depe)2CH2CN]+. In contrast, neither Rh(depe)2Cl nor Rh(dmpe)2Cl (dmpe = Me2PCH2CH2PMe2) react with C02 in acetonitrile, though Rh(dmpe)2Cl does react with C02 in nitromethane to form the analogous nitro-acetate hydride complex, (57). 

Acetyl nitrate (or nitryl acetate, Ac0NO2), prepared from nitric acid and acetic anhydride, reacts with simple acyclic and cyclic alkenes to give complex mixtures of nitro acetates, nitro nitrates and nitroalkenes, which are often difficult to separate12 103, The reaction with unsubstituted cycloalkenes was recently reexamined and a complex mixture of products, including allylic and homoallylic nitroalkenes, 1,2-, 1,3- and 1,4-nitro acetates, and 1,4-nitro nitrates, was identified104. These experimental observations are best accommodated by the proposal, supported by theoretical calculations, that the initial reaction of acetyl nitrate with alkene substrates is a [2 + 2] addition of the nitryl cation to the C-C double bond to form a cyclic cationic intermediate. 

Table 5. //-Nitro Acetates Prepared by Addition of Acetyl Nitrate...

The method appears limited to aryl-substituted acyclic105-109 and cyclic110 alkenes and should be compared with the direct procedure for preparing //-nitro acetates from //-nitroso nitro compounds (Section 7.2.1.5.1). 

The simple diastereoselectivity is dependent on the structure of the alkene syn addition is normally observed with acyclic (Tfj-alkenes, whereas anti addition occurs with acyclic (Z)-alkenes and cyclic alkenes (Table 5). The isomerization of (Z)- to (Ej-alkenes prior to reaction can explain the prevalent or exclusive formation of the syn //-nitro acetate from either isomeric alkene. 

The acidity of carbonyl-containing compounds and their solvent effects have been well documented " ". Typically, enolate formation is less favoured in DMSO than H2O due to lower stabilization of its oxy-anion (i.e. the pATa of the corresponding carbonyl compound in DMSO is higher than in H20). However, under certain circumstances, the reverse can be true , as with certain ammonium salts , for ethyl 2-trifluoromethylsulfonylacetate (21) was found to be more acidic in DMSO [p fa(DMSO) = 6.40 ] than in H20. This unusual behaviour is presumably due to the corresponding enolate existing as a carbanion as opposed to its normal enolic form ". In comparison, for ethyl nitro-acetate (22) and ethyl cynanoacetate (23) the usual trend returns, even... 

Other functional groups may be present during reduction. Aromatic amino ethers are prepared by the same general procedures described above, e.g., 772-aminoanisole (80%) and 2-aminodiphenyl ether (94%). The reduction of o-nitrobenzaldehyde to the sensitive o-aminobenzaldehyde is successfully accomplished by the action of ferrous sulfate and ammonia (75%). m-Dimethylaminobenzaldehyde is formed by reduction of the nitro acetal in aqueous solution with sodium sulfide followed by methyla-tion (74% over-all) or by catalytic reduction of m-nitrobenzaldehyde in... 

The effect of various metal ions on the rate of acid dicarboxylation has been explored. Since the topic is beyond the scope of this chapter, only a brief comment will be made. Metal ions which enter into complexation equilibrium with nitro-acetate ion retard the rate of decarboxylation The kinetic data were... 

This acetate is insoluble in organic solvents, dissolves with decomposition in hydrochloric acid, but is soluble in cold 20 per cent, nitric acid with formation of a nitro-acetate,... 

This compound is formed as a white precipitate from the interaction of ammonium aci-nitro-acetate and mercuric chloride in aqueous solution. It sublimes when carefully heated, detonates when strongly heated, and when ignited burns with a luminous flame,. In bases it dissolves readily, but is almost insoluble in boiling water. Treatment with bromine in potassium bromide solution forms ethyl dibromonitro-acetate, and potassium iodide removes the mercury from the anhydride as mercuric iodide. 

Prager considered the formation of the anhydride to be preceded by the formation of ethyl chloromercuri-aci-nitro-acetate,... 

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