Pyrrolo pyrazole

Diaza-compounds. The pyrrolo-pyrazole derivative (705) is one of the products of the action of acids on the tosylhydrazone H2C=CMe(CH2)2CH=N—NHTos. The reaction of 2,5,5-trimethyl-l-pyr-roline iV-oxide (706) with the ketenimine Ph2C=C=NPh yields the pyrrolo-imidazole (707)/ Pyrazolidin-3-one and 3-chloropropanoyl chloride combine to form the dioxopyrazolopyrazole (708)/ Irradiation of l-(o-iodoben-zoyl)imidazole (709 R=H) produces the indolobenzimidazolinone (710) the... 

H,3H- Pyrrolo[l, 2-c]oxazole-l, 3-dione, 5,6,7,8-tetrahydro-IR spectra, 6, 978 [2.2](2,5)Pyrrolophane, N-aryl-rearrangements, 4, 209 Pyrrolophanes natural products, 7, 764 synthesis, 7, 771 Pyrrolophanes, N-aryl-synthesis, 7, 774 (2,4)Pyrrolophanes synthesis, 7, 771 Pyrrolo[3,4-c]pyran-4-ones synthesis, 4, 288 Pyrrolopyrans synthesis, 4, 525, 526 Pyrrolopyrazines synthesis, 4, 526 Pyrrolo[l, 2-a]pyrazines synthesis, 4, 516 Pyrrolo[2,3-6]pyrazines Mannich reaction, 4, 504 Vilsmeier reaction, 4, 505 Pyrrolo[3,4-c]pyrazole, 1,3a,6,6a-tetrahydro-structure, 6, 976 synthesis, 6, 1019 Pyrrolopyrazoles synthesis, 5, 164 Pyrrolo[l,2-6]pyrazoles synthesis, 6, 1002, 1006 Pyrrolo[3,4-c]pyrazoles reactions, 6, 1034 synthesis, 6, 989, 1043 Pyrrolo[3,4-c]pyrazolones synthesis, 6, 989 Pyrfolopyridazines synthesis, 4, 517 Pyrrolo[l, 2-6]pyridazines synthesis, 4, 297 6/7-Pyrrolo[2,3-d]pyridazines synthesis, 4, 291 2/f-Pyrrolo[3,4-d]pyridazines synthesis, 4, 291 6/7-Pyrrolo[3,4-d]pyridazines synthesis, 4, 291... 

A library of fifteen 6,7,9,9a-tetrahydro-57/-pyrazolo[l,2-tf]pyrrolo[3,4-ir]pyrazole-l,3,5(2/7,3a7/)-triones 712 was prepared by combinatorial stereoselective cycloadditions of compounds 320 to A-substituted maleimides. 

The structure of dihydro-4,5-6//-pyrrolo[l,2-3]pyrazoles 23 and 24 have been determined by X-ray crystallography <2004BML3581>. 

The amino pyrrole 29 derived from the reaction with phenylhydrazine <1998JOC9131> was found to undergo an acid-catalyzed intramolecular condensation with the carbonyl present to give the 3//-pyrrolo[l,2-A pyrazole 30 ring system in a good yield (75%) (Equation 2). 

An easy synthesis of the 2-oxo-2,3-dihydro-l/7-pyrrolo[l,2- ]pyrazole system can be performed by reaction of 1,2-diaza-1,3-butadienes 33 with dialkyl 1,3-acetonedicarboxylate 34 in the presence of potassium carbonate. At first, 1-aminopyrroles 36 was produced by dehydration in the presence of copper(n) trifluoromethanesulfonate. Treatment of these compounds with sodium hydride led to ATZ-substituted 2-oxo-2,3-dihydro-17/-pyrrolo[l,2-A]pyrazole 38. Under the same reaction conditions, and after acidic treatment, NH-BOC-protected 1-aminopyrrole was transformed to NH-unsubstituted 2-oxo-2,3-dihydro-l//-pyrrolo[l,2-A]pyrazole 37 (BOC =/-butylcarbonyl) (Scheme 1). 

The mesoionic compound prepared from L-Pro (83TL1067) reacts with acetylenic compounds to give pyrrolo[l,2-a]pyrazoles after extrusion of carbon dioxide ( Scheme 47). With phenylpropiolic acid, the natural product withasomnine (a) was formed in low yield (7%) together with its regioisomer (b, 5%) (85TL5739). 

Table 11 FVrrolo[2,3-c]isoxazoles (X=0), pyrrolo[2,3-c]isothiazoles (X = S), 2/-/-pyrrolo[2,3-c]pyrazoles (X = NH)...

These methods are limited in scope. Direct thiation has been reported for the transformation of vicinal diketones to [3,4]-annelated thiophenes <1996CHEC-II(7)49>. Thionations and selenations of vicinal halomethyl ketones with thioacetamide or iV,iV-diethylselenopropionamide as sulfur and selenium donors, respectively, have also been reported <1996CHEC-II(7)49>. In a recent example, thieno[3,4-f]pyrazoles 160 were readily prepared from aryl 5-bromomethyl-l//-l-phenylpyrazole-4-yl ketones 159 by reaction with thioacetamide (Equation 35) <1998JHC71>. Additionally, an example of an amination cyclization by reaction of 161 with benzylamine to afford pyrrolo[3,4-i/ thiazole 162 has been described (Equation 36) <1998JHC71>. 

Electrophilic additions to 7t-deficient heterocycles are less common than those to 7t-excessive heterocycles. However, intramolecular electrophilic cyclizations have been used to access the heterocycles of interest in this chapter <1996CHEC-II(7)49>. Recent examples include the preparation of a pyrrolo[2,3-f]pyrazole 165 by acid-catalyzed condensation of 163 and 164 (Equation 37) <1999SC311> and the reaction of 3-(4-pyrazolyl)acrylic acids 166 with excess thionyl chloride in the presence of benzyltriethylammonium chloride (BTEAC) to afford 4-chlorothieno[2,3-f]pyrazole-5-carbonyl chlorides 167 (Equation 38) <2003RJ0893, 2003ZOK942>. In the latter case, the reaction products were readily manipulated to prepare corresponding carboxylic acids, esters, and amides using standard procedures. 

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