Nitro-decarboxylation

Selenophene-2-carboxylic acid, 4-nitro-decarboxylation, 4, 947, 952 Selenophene-2-carboxylic acid, 5-nitro-decarboxylation, 4, 947, 952 Selenophenecarboxylic acids, acidity, 4, 71... 

Whereas nitration of compound (69a) under rather mild conditions (100°C, 1 h) gave the 6-nitro derivative (70a, 96%), nitration for a prolonged period of time (4 h) led to partial nitro-decarboxylation, giving a mixture of 70a and the 3,6-dinitro derivative (70, = Et, = R" = NO2). 

There are examples of ipso attack during the nitration of pyrroles, furans and thiophenes and in the corresponding benzo-fused systems. Reactions resulting in nitro-dealkylation, nitrodeacylation, nitro-decarboxylation and nitro-dehalogenation are to be found in the monograph reactivity chapters of CHEC. Treatment of the 3-azophenylindole (64) with nitric acid in acetic acid at room temperature gives 80% of the 3-nitroindole (65) (81JCS(P2)628). 

Nitromethane, CH3NO2, the first member of the homologous series, can, however, be readily prepared by a special reaction. When equimolecular amounts of sodium nitrite and sodium monochloroacetate are heated together in aqueous solution, the chlorine in the monochloroacetate is replaced by the nitro group, and the sodium nitroacetate thus formed undergoes hydrolysis follow ed by decarboxylation ... 

Cydopentane reagents used in synthesis are usually derived from cyclopentanone (R.A. Ellison, 1973). Classically they are made by base-catalyzed intramolecular aldol or ester condensations (see also p. 55). An important example is 2-methylcydopentane-l,3-dione. It is synthesized by intramolecular acylation of diethyl propionylsucdnate dianion followed by saponification and decarboxylation. This cyclization only worked with potassium t-butoxide in boiling xylene (R. Bucourt, 1965). Faster routes to this diketone start with succinic acid or its anhydride. A Friedel-Crafts acylation with 2-acetoxy-2-butene in nitrobenzene or with pro-pionyl chloride in nitromethane leads to acylated adducts, which are deacylated in aqueous acids (V.J. Grenda, 1967 L.E. Schick, 1969). A new promising route to substituted cyclopent-2-enones makes use of intermediate 5-nitro-l,3-diones (D. Seebach, 1977). 

One effective method for synthesis of tryptophan derivatives involves alkylation of formamido- or acetamido- malonate diesters by gramine[l,2]. Conversion to tryptophans is completed by hydrolysis and decarboxylation. These reactions were discussed in Chapter 12. An enolate of an a-nitro ester is an alternative nucleophile. The products can be converted to tryptophans by rcduction[3,4],... 

The intermediacy of an aci-nitro compound has been proposed for the sulfuric acid cyclization of o-nitrophenylacetic acid to yield a mixture of 2,1-benzisoxazole and 2,1-benzisoxazole-3-carboxylic acid. The acid does not decarboxylate under the reaction conditions. The proposed aci-nitro intermediate cyclized to an A/ -hydroxy compound which decomposed to the products (Scheme 179) (70JCS(C)2660). 

Finally, certain 3-substituted compounds can be prepared by utilizing the - meta) directing powet (cf. Section IV,B) of some groups in the 2-position which afterward can be removed. 3-Nitrothiophene is prepared by nitration of 2-thiophenesulfonyl chloride and by removal of the sulfonic acid group of the 4-nitro-2-sulfonyl chloride formed with superheated steam. Another approach to 3-nitrothio-phene is to nitrate 2-cyanothiophene, separate the 4-nitro-2-cyano-thiophene from the 5-isomer, hydrolyze, and decarboxylate. A final method of preparation of 3-nitrothiophene is by simultaneous de-bromination and decarboxylation of 5-bromo-4-nitro-2-thiophene-carboxylic acid obtained through the nitration of methyl 5-bromo-2-thiophenecarboxylate. 

The quindoline 224 may be prepared by the condensation of indoxyl-2-carboxylic acid with 6-aminopiperonaldehyde in the presence of hydrochloric acid, when decarboxylation and cyclization take place. Nitric acid oxidation of 224 gave an unstable nitrodicarboxylic acid which decarboxylated readily to a nitromonocarboxylic acid formulated as 8-nitro-8-carboline-3-carboxylic acid (225). ... 

Nitration of l,8-iiaphthyridiii-2,5(lH,8H)-dioiie (55a) and some of its derivatives (55b-55d) was studied by Carboni and coworkers (72GCI253). Tliey observed the formation of the 3-nitro derivatives (56a/56b) from (55a/ 55d) under more severe conditions from (55b/55c) the 3,6-dinitro derivatives (57a/55b) are obtained. In the case when a carboxyl group is present, decarboxylation is observed. 

The furazan ring is stable under the conditions used to reduce the nitro group to the amine (Scheme 6). Thus, on treatment of compound 19 with SnC in HCl, the nitro group was reduced and the cyano group underwent hydrolysis and decarboxylation yielding salt 20 (30G721). 

Active methylene compounds also displace the nitro group at the furazan ring. Thus, 3,4-dinitrofurazan reacted with the sodium salt of ethyl (3-oxo propionate or related compounds in the presence of a crown ether to give the corresponding ester, which was readily hydrolyzed and decarboxylated (92UP1) (Scheme 146). 

CotLespondingly, tlie catalytic 1,4-addition of dialkylzinc reagents to 3-nitro-iimarin 89 iSdieme 7.24), witli a fixed irans orientation of tlie aiyl and nitro oiips, proceeds witli excellent yidds 190-99 96), bigli diastereoselectivity Id.r. up to ), and enantiosdectivities of up to 9296. Hydrolysis of tlie lactone moiety in 90 IS accompanied by decarboxylation, providing an asymmetric syntliesis of /J-aiyl-troalkane 91. 

ETHYL BENZOATE VIA THE NITRO-SOAMIDE DECOMPOSITION, 47, 44 Decachlorobi-2,4-cyclopentadienyl, dechlorination by triisopropyl phosphite, 46, 93 a-Decalones, 46, 82 Decanoyl fluoride, 46, 6 Decarboxylation, in formation of couma-rone from o-formylphenoxyacetic acid, 46, 28... 

Diazotization of the amines 1, obtained by catalytic hydrogenation of the corresponding nitro compounds, gives the esters 2 directly. Alkaline hydrolysis of the latter yields the acids 3, which can be decarboxylated to l//-l,2,5-benzotriazepin-4(5/7)-ones 4. Yields were not reported.372... 

Here too there is an enol that tautomerizes to the product. The mechanism is illustrated for the case of P-keto acids, ° but it is likely that malonic acids, a-cyano acids, a-nitro acids, and P,y-unsaturated acids behave similarly, since similar six-membered transition states can be written for them. Some a,P-unsaturated acids are also decarboxylated by this mechanism by isomerizing to the p,y-isomers before... 

This procedure has been used in the preparation of other nitrostyrenes in the following yields o-nitrostyrene (40%),2 / -nitrostyrene (41%),2 and 3-nitro-4-hydroxystyrene (60%).2 A better procedure for more volatile styrenes involves simultaneous decarboxylation and codistillation with quinoline from the reaction flask. This method has been used to prepare the following styrenes o-chlorostyrene (50%),3 4 m-chlorostyrene (65%),4 -chlorostyrene (51%),4 m-bromostyrene (47%),4 o-methoxystyrene (40%),4 -methoxystyrene (76%),4 m-cyano-styrene (51%),3 and j -formylstyrene (52%).9... 

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