L- -cyclopropan

Intramolecular [2 + 2] photocycloadditions have been used successfully for the syntheses of (polycyclic) cage compounds. Recent examples of such reactions are the formation of pentacyclo[5.4.0.02 6.031°.05 9]undecane-8,ll-dione-4-spiro-l-cyclopentane,55 hexacy-clo[7.4.2.01,9.03,7.04 14.061s]pentadeca-10,12-diene-2,8-dione-5-spiro-l -cyclopropane,56 pen-tacyclo[5.4.0.02 6.031°.04 8]undecane57 and pentacyclo[6.4.0.02 7.03 12.06 9Jdodeca-4,10-diene.58 Irradiation of benzoquinone tetrahydropentalene adducts afford cage compounds which are easily converted to angular tetraquinanes.59... 

Cyanospiro[2-pyrazoline-5,l cyclopropane] 228 underwent unusual transformations into 3(5)-cyano-5(3)-(2-hydroperoxyethyl)pyrazoles 229 in the presence of atmospheric oxygen, and these were converted into (2-hydroxy-ethyOpyrazoles 230 with sodium pyrosulfite in aqueous methanol (Scheme 15) <2004RCB2257>. 

A new synthesis of enantiomerically pure 2-amino-3-phenyl-l-cyclopropane-phosphonic acid, a constrained analogue of phaclofen (267), has been described. The sulfoxide (268) of (S) configuration was found to undergo cyclopropanation... 

Dihydrothiophene 1,1-dioxide underwent addition of dichlorocarbene generated from bro-modichloromethyl(phenyl)mercury to give the product 5 in 23% yield only, after troublesome isolation [this product can be obtained in good yield from l,l-dichloro-c .9-2,3-(di-chloromethy l)cyclopropane]. ... 

On reaction of spiro[bicyclo[2.1.0]pentane-5,l -cyclopropane] with 4-phenyl-4/f-l,2,4-triazole-3,5-dione the bridge was cleaved and cycloaddition to the N-N double bond took place giving 4-phenyl-2,4,6-triazaspiro[cyclopropane-l,10 -tricyclo[5.2.1.0 ]decane-3, 5 -dione] in quantitative yield. 

It is noteworthy that irradiation of tetracyclo[6.2.0.0 . 0 ]decan-9-one resulted in cycloreversion and formation of ketene and vinylcyclopropane tricyclo[5.1.0.0 ]oct-5-ene instead of ring cleavage and decarbonylation. A C-C double bond a to a cyclopropane ring also resulted when spiro bicyclo[2.2.1]hept-5-ene-7,l -cyclopropane -2-one eni/o-epoxide underwent a deep-seated rearrangement upon irradiation through Corex to give 5-oxo-spiro[2.4]hept-6-ene-4-ylacetaldehyde in 50% yield. ... 

Dispiro[cyclopropane-l,2 -bicyclo[2.2.0]hexane-3, l"-cyclopropane] (8) Single Procedure ... 

When the analogous 1 -methylene-2-phenylcyclopropane was heated to 140 "C the starting material remained unchanged. Under more forcing conditions (190°C, 16 h) a mixture of dimeric products, including cis- and fra s-7,8-diphenyldispiro[2.0.2.2]octane and T,2, 3, 4 -tetrahydro-2 -phenyldispiro[cyclopropane-l,T-naphthalene-3, l"-cyclopropane], was obtained but no in-dene derivative could be detected. ... 

Tricyclo 2.1.1.0 lhexan-<2-spiro-l>-cyclopropan-< 2-spiro-2>-tricyclo[2.1.1.0 ]hexane... 

Bei Homofulvenen werden lichtinduzierte Isomerisierungen zu Methylen-cyclo-hexadienen l, Cyclopropan- (1 -spiro-5)-cyclopentadienen 2 5 und substituiertcn Benzolen1-4 beobachtet. 

Ring-Fluorinated Pyrazolines Fluorinated olefins undergo 1,3-dipolar cycloaddition reactions with diazomethane to produce fluorinated pyrazolines. In some cases, these are not isolated but are directly converted to fluorinated cyclopropanes by extrusion of nitrogen, either thermally or photochemically. For example, reaction of a series of 2-aryl-3-fluoroacrylates with diazomethane produced intermediate fluorinated pyrazolines that were ponverted to a series of 1-aryl-l-cyclopropane carboxylates by irradiation at 3500 A (Fig. 3.75). The esters in turn were... 

Trispiro[cyclopropane-(l,3 ) tricyclo[2.2.1.0 ]-heptane-(5, l")-cyclopropane-(7, l")-cyclopropane] T rishomotriquinacene T rishomobullvalene Congressane... 

The Spiro bridge of spiro(bicyclo[2.2.1]hept-2-ene-7,l -cyclopropane) (7-spiro-(CH2)2-NB) is less sterically demanding than the syn-methyl substituent of iy -7-MeNB, and yields greater than 90% of poly(7-spiro-(CH2)2-NB) (Scheme 20.11) are obtained with RuCb (H20)3 (12 1 toluene/EtOH, 18 h, 75 C) and WCl6/Ph4Sn (toluene, 15 h, 20 °C). Samples of poly(7-spiro-(CH2)2-NB) made using both catalysts are atactic and contain predominantly trans olefin linkages (85% for the W-based catalyst and 95% for the Ru catalyst). ... 

The catalytic cleavage of two C-C single bonds in reaction of spiro[bicyclo[2.2.1 ]hept-2-ene-7,l -cyclopropane] with Pt(II) catalysts to l,2,4,7,7a-pentahydroindene has been reported in which an initial masked C-H bond activation initiates successive C-C bond cleavage events (Scheme 151). ... 

---