Spiro-pyrazolines

Spiro-pyrazoline derivatives (18) are obtained smoothly from 16-methy-lene-17-ketones (17). ° The sole products formed from (18) by pyrolysis or cleavage in the presence of boron trifluoride etherate, are the 16-spiro-cyclopropyl steroids (19). ... 

The spiro-pyrazoline-ketone (342) expels nitrogen when treated with either boron trifluoride etherate or acetic anhydride-pyridine, giving the cyclopropyl ketone (343)." ... 

The route can be modified to make optically active amino acids.Hence addition of diazomethane to the dioxopiperazine 14 [itself prepared from (Z)-4-benzylidene-2-methyloxazolone and L-proline] gave a 70% yield of the spiro-pyrazoline 15 (ratio of diastereomers 95 5). Separation of the major diastereomer and photolysis gave a 90% yield of the cyclopropane 16, which on hydrolysis gave (-l-)-17 in 70 % yield. 

The 1,3-dipolar cycloaddition reactions of nitrilimines with cjco-heterocyclic enones have been reviewed. The use of these reactions to synthesize spiro-heterocycles containing chiral centres is discussed. The catalytic 1,3-dipolar cycloaddition of nitrilimines with methyleneindolinones produced spiro[pyrazolin-3,3 -oxindole] adducts in high yields (98%) and high enantioselectivity (99% ee). ... 

A variety of substituted diazoalkanes have been examined. Rodina et reported formation of a spiro pyrazoline 31 from the cyclic diazoketone 30. The product on further heating to 141°C loses 1 mole of N2 to yield a spiro cyclopropane derivative 32. 

Dipolar cycloadditions of 1,3-diphenylnitrilimine with various fulvenes, for example, 2,3,4,5-tetraphenylfulvene, 9-benzalfluorene, and 6,6-diphenylfulvene, providing a series of spiro-pyrazolines, were studied by Dhar and Ragunathan (Scheme 7.7) [8]. Most of these 1,3-dipolar cycloadditions took place across the exo-cycVtc double bond to give the spiro-pyrazoline derivatives, the exception being 6,6-diphenylfulvene 27, which underwent reaction at the endo-cycMc site to afford the fused pyrazoline derivative 29. 

Cyclic diazoalkanes have been used to generate spirocyclopropanes via ring contraction of pyrazolines formed in the initial cycloaddition step. Two novel examples are the transformation of 3-diazo-2-nitromethylenepiperidine (16) into 5-aza-spiro[2.5]octane 17 (45) and the conversion of 1-diazo-2-methylenecyclo-propane (18) into methylene-spiro[2.2]pentane 19 (46) (Scheme 8.6). Related reactions have also been reported for diazocyclopropane (47) and diazospiropen-tane (48). 

In contrast to the reaction products of the 1,3-dipolar cycloaddition to linear enones (chalcones and their derivatives), spiro- 1-pyrazolines 25-28 are stable heterocycles. Their isomerization into spiro-2-pyrazolines 29-31 can be carried out under acidic conditions at room temperature for 24 h in the case of the cis isomers, and for more than 1 month in the case of trans isomers [30, 41, 42, 43]. 

The salicylaldehydes commonly used have nitro, alkoxy, or halogen substituents, and need no further comment. Some unusual ones have cationic substituents 3-, 4- and 5-methylthio- and dimethylaminosalicylaldehydes have been prepared and methylated to the corresponding dimethylsulfonium and trimethylammonium salicylaldehydes. 1012 The salicylaldehyde substituted in the 4-position with a 3,5-diphenyl-2-pyrazolin-l-yl group gives a series of BIPS and spiro(dipyrans) having highly fluorescent spiro forms and nonfluorescent open forms, which is the reverse of the usual situation. 13... 

Alloum et al. (1998) described new spiro-rhodanine-pyrazolines (2) by 1,3-dipolar addition of DPNI to some 5-arylidenerhodanines on alumina or KF/alumina in dry media under microwave irradiation. In all the cases, the yields were quantitative and obtained in 10 min whereas no reaction occurred under classical thermal conditions. These observations showed some specific role of microwave irradiation in product synthesis. 

Alloum, A.B., Bakkas, S., Bougrin, K., and Soufiaoui, M. 1998. Synthese de nouvelles spiro-rhodanine-pyrazolines par addition dipolaire-1,3 de la diphenylnitrilimine sur quelques 5-arylidbnerhodanines en milieu sec et sous irradiation micro-onde. New Journal of Chemistry, 22 809-12. 

Numerous unsuccessful attempts to synthesize cyclopropanethione have been reported. Thermal or photochemical generation of the C3H4S species from different sources always leads to allene episulfide. Some representative experiments include (a) in vacuo pyrolysis of the sodium salt of 2,2,4,4-tetramethylthietanone tosylhydrazone (4) into the stable tetramethylallene episulfide (S), (b) pyrolytic extrusion of nitrogen from perfluorinated thiadiazoline 6, (c) in vacuo pyrolysis of spiro compound 8 into methylenethiirane (3), (d) the flash vacuum pyrolysis-microwave spectroscopic approach applied to spiro compounds 9 and 10, (e) pyrolysis of anthracene adduct 11 and tosylhydrazide salt 12, (f) thermolytic nitrogen extrusion from pyrazoline-4-thione 13, thermolysis of tetramethylallene episulfide (5) or pyrazoline 13 in dig-lyme solution, and photolytic nitrogen extrusion from pyrazoline 13, ° (g) thionation of methylenecyclopropanone 15, and (h) reaction of donor-acceptor substituted allenes 18 with elemental sulfur. ... 

The 1,3-dipolar addition of diphenylnitrilimine 833 to some 5-arylidenerhodanines 64 on solid inorganic supports in dry media under MWI gave the spiro-rhodanine-pyrazolines 834 in 75-90% yields (Scheme 157) (98MI1). 

DipoIar cycloadditions of fiiUerenes gave expected products. In cycloadditions with azides triazolines 25 were formed, while with diazo compounds such as 9-diazofluorene 22, spiro cyclopropane products 24 were directly prepared. In this case initially formed pyrazoline intermediate 23 was not isolated (Scheme 7.6) [13]. 

The full details of oxa-bis- and oxa-tris-a/ic-homobenzene syntheses, cw-aza-bis-and cis-aza-tris-a-homobenzene and cis-aza-tris-a-homotropilidene synthesis, and the decomposition of spiro[fluorene-9,3 -indazole] have become available, and there have been a number of routine applications of pyrazoline decomposition for cyclopropane synthesis. ... 

S-Dihydtoisoxazole derivatives, e.g. 110, could be obtained from iodo-tosylates such as 109 as shown in Scheme 22. They have potential for production of chain extended compounds, e.g. 111. as the nitro-group can be displaced by carbanionic reagents. Addition of diazomethane to 3 -deoxy-3 -methylene-nucleosides yields 3 -spi>o-pyrazoline derivatives whidi can be converted to 3 -spiro-cyclopropane analogues with loss of nitrogen. ... 

Keywords Isatins, malononitrile, 2-pyrazolin-5-ones, sodium bicarbonate, grinding, room temperature, solvent-free, one-pot multicomponent reaction, heterocycles, spiropyranyl-oxindoles, spiro[indoline-3,4 (l// )-pyrano-[2,3-c]pyrazol]-2-ones... 

Mamedov VA, Murtazina AM, Gubaidulhn AT, Khafizova EA, Rizvanov IKh, Litvinov lA (2010b) Benzimidazoles and related heterocycles 8. Acid-catalyzed rearrangement of 3-aryl-l 7f-spiro[2-pyrazoline-5,2 -quinoxalin]- 3 (4 77)-ones as a new efficient method for the synthesis of 2-(pyrazol-3-yl)benzimidazoles. Russ Chem Bull, Int Ed 59(8) 1645-1655. doi 10.1007/ S11172-010-0289-7... 

A second common reaction of sulphonium ylides is Michael addition to ajS-unsaturated carbonyl compounds, giving cyclopropanes. This reaction forms the basis of a cyclopentene synthesis starting from sulphonium allylide (14). Other recent examples include the preparation of spiro[cyclopropane-l,4-A -pyrazolin]-5 -one derivatives (15) and cyclopropyl-ulose (16). Un-... 

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