2-Aminofuran

Aminofurans cannot be prepared by reduction of 2-nitrofurans or by hydrolysis of 2-acetamidofurans. The latter are prepared by the reduction of 2-nitrofurans in the presence of acetic anhydride. Benzofuranone (161) and not 2-aminobenzofuran is obtained from tin and hydrochloric acid reduction of 2-nitrobenzo[h]furan (160). 

Aminofurans substituted with electron-withdrawing groups e.g. NO2) are known and 3-amino-2-methylfuran is a relatively stable amine which can be acylated and diazotized. 2-Amino-3-acetylfurans are converted into 3-cyano-2-methylpyrroles on treatment with aqueous ammonia. This transformation is a further illustration of the relative instability of the amino derivatives of five-membered ring heterocycles compared with anilines (Scheme 67) (781003821). 

Synthesis ol 2-aminofurans (thiophenes, pyrroles) by cortdensation of malononitnles with ketones. 

Ketoamides can participate in a variation of the Paal-Knorr condensation to yield 5-alkyl-2-aminofurans. Boyd described the cyclization of 1,4-ketoamides 91 upon exposure to acetic anhydride and perchloric acid to yield imminium salts 92 that furnished aminofurans 93 after treatment with triethylamine. ... 

MONOCYCLIC AMINES WITH ONE HETEROATOM 2-Aminofurans 66JHC202... 

ACS692). However, using suggested conditions the formation of 2-aminofurans 87 is predominant (Scheme 24). 

The 1,4-diketone may be used in protected form, e.g. as a ketal. 3,4-Diethoxycarbonylfuran (109) is obtained from the acetal (108) with sulfuric acid in 68% yield (54100671). 2-Aminofurans are also obtained by cyclization of 8-ketonitriles (90MI207-01). 

Carbene complexes of Fe and Co carbonyls are also prepared. Unlike the Cr carbene complexes, no cyclopropanation of alkenes occurs with these carbene complexes. Furans are formed by the reaction of alkynes involving rearrangement of methoxy group. The 2-aminofuran 323 is formed by the reaction of the dimethylaminocarbene complex 319 of Fe carbonyl, via rearrangement of the amino group. Under CO pressure, pyrone 324 is the main product [97]. In these reactions, the... 

A number of important families of heterocycles belong to this class and many of the important systems are oxo derivatives. 2-Hydroxyfuran 64 exists almost exclusively as the equilibrating 3H- and 5//-furan-2-one tautomers 66 and 67. Tautomerism favoring the nonconjugated isomers also occurs in hydroxypyrroles and hydroxythiophenes. Similar behaviour is observed with simple amino derivatives 2-aminofuran 65 is too unstable to be detected <2006AHC (92)1 >. The 3-oxo tautomer 68 is the preferred form of 3-hydroxyfuran. 

Both 2- and 3-nitrothiophenes are reduced by tin and hydrochloric acid to the corresponding aminothiophenes. Reduction of 2,5-dibromo-3,4-dinitrothiophene gives 3,4-diaminothiophene as a stable crystalline solid. 2-Acetamido-furans are prepared by the reduction of 2-nitrofurans in the presence of acetic anhydride. 2-Substituted 5-nitrofurans can be reduced to the S-aminofurans by an electrochemical method. Although catalytic reduction gives 2-aminofurans only in low yields, they can be trapped using ethyl ethoxymethylenecyanoacetate or ethoxymethylenemalononitrile. Benzofuranone 412 and not 2-aminobenzofuran is obtained from tin and hydrochloric acid treatment of 2-nitrobenzo[ ] furan 411. 

The employment of activated cyanomethylene compounds (e.g., malononitrile) for condensation with -amino carbonyl derivatives (e.g., the protected aminoacetaldehyde 184) provides 2-aminopyrroles 185 (Scheme 101) <2004OL2857>. In a comparable fashion, the condensation of -mercapto carbonyl compounds with malononitrile derivatives provides 2-aminothiophenes (Scheme 102) <1979LA328>. Similarly, 2-aminofuran-3-nitriles can be obtained by base-catalyzed condensation of -hydroxy ketones with malononitrile < 1966GB 1002>. 

A 2-aminofuran was converted into 4,4 -bipyrazole by reaction with two molecules of hydrazine <06TL8965>. Hydrogenation of 2-amylfuran under 5 atm of H, as catalyzed by 10% Rh/Cat80 °C in water provided 2-amyltetrahydrofuran in 90% yield <06SL1440>. An advance in the area of enantioselecti ve hydrogenation of furans, as reported by Pfaltz, is the hydrogenation of... 

Indolines. Indolines are readily < reaction of 2-aminofurans in which tfai cycloaddition is promoted by LiCIO. ... 

As in the furanol series, there is a problem of tautomerism with fura-namines. In general, aminofurans can exist to some extent as imines acid hydrolysis frequently eliminates ammonia. Meinwald and his colleagues have studied such 2-aminofuran hydrolyses and found them to give not the expected butenolides but dimers.215... 

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