Pyrazolo pyrazoles, 1,6-dihydro

Arnino-6,7-dihydro-l //,5//-pyrazolo[ 1,2- pyrazol-l-onc 269 is easily obtained in 57% yield as its hydrochloride by acid-catalyzed ring closure of nitrile 268 using hydrochloric acid. A better yield is described for the synthesis starting from the N-protected compound 267. Treatment with hydrochloric acid provides crystalline hydrochloride of 268, which is then cyclized by heating in ethanol (Scheme 33) <2001JHC613>. 

Isocyanides and dialkyl acetylenedicarboxylates in the presence of 2,4-dihydro-3//-pyrazol-3-ones 344 in acetone at ambient temperature undergo a smooth 1 1 1 addition reaction to produce highly functionalized 7-oxo-17/,7H-pyrazolo[l,2-tf]pyrazole derivatives 345 in 69-81% yields (Equation 47) <2005T3963>. 

Besonders wichtige Kuppler sind 4-Amino-pyrazole mit unsubstituierter 5-Stellung. Die aus ihnen resultierenden Azo-Verbindungen sind grungelbe Farbstoffe, die auch zur Syn-these von optischen Aulhellern vom 2,4-Dihydro--Typ die-nen1 ... 

Another interesting reaction of benzoxazines 114 (115) is the reductive opening of the oxazine ring with simultaneous dehydrogenation of the pyrazoline moiety [170]. This process is carried out in a KOH suspension of a mixture of dimethyl sulfoxide and dimethylformamide. For instance, this treatment involving 2,5-diary l-l,10b-dihydro-177-pyrazolo[l,5-c]benzo[e]-l,3-oxazines 116 leads to the formation of pyrazoles 117 (Scheme 2.32). Similar disproportionation reactions have also been described for some bezopiranes, for example, pyrazole derivative 118 [91, 170]. 

The new pyrazolo[l,5-tf][l,3,5]benzoxadiazocine heterocyclic ring system 123 was prepared by cyclization of 4,5-dihydro-3-methyl-5-(2-hydroxyphenyl)-17/-pyrazole-l-carboximidamide with triethyl orthoformate. A reaction mechanism involving re-esterification of triethyl orthoformate with phenolic hydroxyl of the additional equivalent of hydroxyphenyl pyrazoline was proposed to explain the formation of the product with an additional guanidine moiety (Equation 17 <2002J(P1)1260>). 

Aldehydes, arylideneanilines, carboxylic acids and orthoesters have been used as one-oarbon units for binding the two amino functions of 4-amino-l-alkyl-3-propylpyrazole-5-oarboxamide to give l,6-dihydro-pyrazolo[4,3-<7]pyrimidin-7-ones <05MC619 05JHC751>. A modified efficient synthesis of variably substituted pyrazolo[4,3-<7]pyrimidm-7-ones has been described using a pyrazole-5-carboxylic acid, which was selectively brominated at position 4 and then converted into the carboxamide. Microwave irradiation gave better yields in the conversion of the carboxamides to pyrazolo[4,3-J]pyrimidinones <05JHC1085>. 

In 4-Oxo-4,5-dihydro-lH-Pyridazin-Ring mit Natrium-ethanolat zum lH-Pyrazol transformiert756 z.B. ... 

Methyl-2-(4-inethyl-phenyl)-4-phenyl-2,4-dihydro- (r = CHj-c H.,)178 Ei-a-25i4 2,91 g (0,01 mo ) 5-Amino-3-methyi-4-(4-methyl-phenylazo)-l-phcnyl-1 H-pyrazol werden in 10 m/ DMF mit 1 g (0,0052 mol) Kupfer(II)-acctat 1 h auf 90-95° erhitzt, dabei wird ein Luftstrom durch... 

Substituierte 3-Amino-4-carboxy-lH-pyrazole und Carbonsaure-chloride oder Acetanhydrid cyclisieren zu 2,4-Dihydro[3,4-d]-l,3-oxazinen>2146,2146a z.B. ... 

Aus 2,4-Dioxo-l,2-dihydro-4H-3,l-benzoxazin wird beim Verschmelzen mit 3(5)-Hydroxy-5(3)-methyl-lH-pyrazol das Benzo-analoge des Pyrazolo[l,5-a]pyrimidins gebildet2180. 

Substituierte 3-Amino-lH-pyrazole kondensieren mit 3-Oxo-butansaure-ester-Derivaten liber die Amino-Gruppe und die 2-Position des Pyrazol-Rings zu 5-Chlormethyl-7-hydr-oxy-1,3a-dihydro-[Pg.683]

Die Umsetzung von 3(5)-Amino-lH-pyrazol mit Aryl-cyanaten in Aceton fuhrt bei Tcmpera-turen von <30° zu 4-Aryloxy-2,2-dimethyl-l, 2-dihydro-[Pg.693]

Benzyl-4-ethoxycarbonyl-5-(2-phenyl-ethenyl)-l H-pyrazole cyclisieren beim Erwarmen in Polyphosphorsaure unter intramolekularer elektrophiler Alkylierung zu 9,10-Dihydro-5H-1974a. 

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