3-Amino-benzo furans

An efficient approach for asymmetric syntheses of benzo[ ]furan-l-alkylamines was developed by reaction of 2-lithiated benzoMfuran with aldehyde-SAMP-derived hydrazones (SAMP = (3 )-(—)-l-amino-2-methoxymethyl-pyrolidine Equation 84). In this way, an efficient synthesis of hydrazine 91 was achieved <2004TA747>. 

Hydroxymethyl-4,8-dimethylfuro[2,3-/j]chromen-2-one was realized in an efficient manner via a Claisen rearrangement of 4-(hydroxybut-2-ynyloxy)-4-methylchromen-2-one as depicted in the following scheme. Other examples with substitution of hydroxyl and with other substituents, such as chloro, amino, acetoxy were also reported <06JHC763>. A new approach for the synthesis of oxygenated benzo[ ]furans was developed via epoxidation and cyclization of 2 -hydroxy stilbene <06T4214>. 

Benzo[l)]furan-6-carbonitrile and 6-cyanobenzo[l>]furan-2-boronic acid pinacol ester were prepared in the presence of Cu. (13SC1974) 2-Substituted benzo[ ]furans were synthesized by employing easily accessible A/-tosylhy-drazones and o-hydroxy or o-amino phenylacetylenes as substrates. (13OBC1490) One-pot access to either 2-naphthols or benzo[l>]furans via the aerobic Wacker-type oxidation/intramolecular aldol cyclization was accomplished. (13T1532 ) 5,5-Disubstituted-2,2 -bisbenzofuran derivatives were produced by treatment of 4-substituted-2-(2-trimethylsilylethynyl) phenyl tert-butyldimethylsilyl ether analogues with CuCl as a catalyst (13TL2655). 

Reaction of 6 with tertiary and also certain secondary enamines leads to the formation of 3-amino-benzo[fc]furan derivatives 174. This is formed not by Michael addition, but via geminate radical ion pair formation with subsequent generation of an oxygen-carbon bond to yield benzofurans. The products were investigated with regard to inhibition of purified human protein kinase CK2 and their general cytostatic activity (Scheme 57,llBOM2666). 

Benzo[c]furan, 6-amino-1,3-dihydro-1 -phenyl- H NMR, 4, 574 <75JA5160>... 

Benzo[b]furan, 2-alkyl-2,3-dihydro-synthesis, 4, 680 Benzo[b]furan, 2-amino-synthesis, 4, 710 Benzo[b]furan, 3-amino-tautomerism, 4, 38 Benzo[b]furan, 2-amino-2,3-dihydro-applications, 4, 708... 

Benzo[6]furan-2-carboxylic acid, 2-amino-tautomerism, 4, 648... 

Benzo[b]furan-3-carboxylic acid, 2-amino-esters... 

Phthalides — see Benzo[c]furan-l (3H)-one Phthalimide, 2-amino-pyridazine synthesis from, 3, 53 Phthalimide, N-cyclohexylthio-as vulcanization accelerator, 1, 404 Phthalimide. methylidine-polymerization, 1, 273 Phthalimide, N-(trichloromethylthio)-biocide, 1, 399 Phthalimide, 1-vinyl-polymerization, 1, 273 Phthalimide, N-vinyl-copolymer... 

Since Woodward s work on the synthesis of chlorophyll a (60JA3800) it is known that the intrinsic unstable thioformyl moiety can be stabilized by the delocalization effect of heterocyclic systems. Recently the synthesis of 2-amino- and 3-aminothioformylthiophenes (and furans) and the corresponding benzo derivatives (Scheme 19) has been reported (96S1185). These compounds exist as amino tautomers (91S609 96S1185). 

These include useful ring syntheses for benzo[h]-fused compounds. The sequence (87) — (88) — (89) has been extensively applied to obtain benzo[h]furans (48JCS2254), benzo[h]thiophenes (31LA(488)259) and, less frequently, indoles (27JCSI937). Corresponding nitriles afford 3-amino derivatives, e.g. (90) —< 3-amino-2-aroylbenzofurans. 

Aminobenzo[6]furan-2-carboxylates and 2-acylbenzo[6]furan-3-amines exist as the amino tautomers. 3-Pyrrolidinobenzo[6]furan is available from benzo[Z>]furan-3(2//)-one (74RTC321). 

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