A facile synthetic approach to the indeno[1,2-b]pyrrole system by cycloaddition of enamines to ninhydrin

Catalyst-free mechanochemistry as a versatile tool in synthetic chemistry: a review

“…25 In this regard, Kaupp et al developed a catalyst, solvent-free mechanochemical (ball milling) procedure for the Knoevenagel reaction of stoichiometric quantities of barbituric acid/its derivative ( 14) or Meldrum's acid (15) with solid aldehydes (13) to access polyfunctionalized olefins 16 and 17 (Scheme 8). 26 The reaction of dimedone (18) with solid aldehyde (13) produced the bis-enol derivative 19 (Scheme 9), involving Knoevenagel condensation of 13 and 18 followed by a nucleophilic addition (Michael addition) of 18 with the resultant Knoevenagel condensation product. A Michael addition reaction was also reported between benzylidinebisnitriles (20) [obtained by the Knoevenagel condensation reaction of 13 and malononitrile (21)] with 18 to produce 2-aminopyranes, 22 (Scheme 10).…”

“…Scheme 10 Catalyst, solvent-free mechanochemical cyclization reaction of Knoevenagel condensation product (20) with dimedone (18).…”

Quantitative Reaction Cascades of Ninhydrin in the Solid State

“…Compound 15 had been synthesized in solution, but only in 82 % yield. [12] The structure of 15 is derived from the 1 H NMR data which exclude a symmetric diketo spiro [5,4]azaoctadien structure. DFT calculations at the B3LYP/6-31G* level give the imine tautomer (in brackets) 5.86 kcal mol À1 higher in energy than the enamine tautomer 15.…”

The chemistry of .beta.-enaminonitriles as versatile reagents in heterocyclic synthesis

“…2 reacts with ethyl benzimidate 115 to give 4-amino-6-methyl-2-phenylpyrimidine (116) An important herbicide intermediate was obtained by treating 2 with methanol at room temperature to give the imino ether 120. The latter was treated with cyanamide at 40 °C to give 2-amino-4-methoxy-6methylpyrimidine (121) A general method for the synthesis of a wide variety of 2-substituted 4-amino-6-methylpyrimidines 134 from nitriles 133 by using tetramethylammonium hydroxide as a catalyst was reported by Smithwick et al 113 The reaction involves addition of enamino amino function to cyano group in the nitrile 133 Enaminonitriles such as 138a-c yield 2-bromopyrimidine 141 when treated with cyanogen bromide.…”