Norcarene derivative

Several norcarene derivatives were shown to undergo dehydrogenation with ring opening to form the more extended % system of cycloheptatriene. Thus, irradiation of chloranil in the presence of tricyclo[4.4.1.016]undeca-3,8-diene (45) gave rise to bicyclo[4.4.1]undeca-l,3,6-8-tetraene (46), while the quinone was reduced to the corresponding hydroquinone [229, 230]. 

When oxidizing agents are used additional activation is not required thus, lead(lV) acetate reacted with a 2-methylprop-l-enyl group by concomitant oxidation and rearrangement and a 2-norcarene derivative reacted similarly with selenium dioxide. Rearrangement accompanied by oxidation also occurred on reaction of derivatives of tricyclo[3.2.1.0 ]oct-6-en-8-one with potassium rert-butoxide in dimethyl sulfoxide. " ... 

Spectra and Theoretical Chemistry of Oxirans.—Electrophilic additions to a series of norcarene derivatives to yield the oxirans (84 R = H, = Me), (84 R = Me, R = H), and (85) have been described. Proton n.m.r, spectra and A -ray structures for these oxirans are given, and their conformations have been established. The chemical shifts and coupling constants for the H and n.m.r. spectra of a series of cis- and tran5-epoxystilbenes have been reported. ... 

Sensitized irradiation of (398) below — 30 °C gave only (399) photo-isomerization occurs at higher temperatures, and the formal ( 2 + 2 -l- 2) process probably involves biradical intermediates. Singlet rearrangements appear to be involved in the photochemical conversion of (400 both syn and anfi-isomers) in methanol into naphthalene, methyl 1-naphthylacetate, and 7-carbomethoxy-2,3-benzonorcaradiene (the major product). The anti-chloroketone (401), but not its sy -isomer, likewise underwent photorearrangement to the norcarene derivative, thus illustrating the stereospecificity. 

The carbenes derived from bicyclo[3,l,l]heptan-6-one and bicyclo[3,2,0]heptan-6-one by pyrolysis of their tosylhydrazone sodium salts, both rearrange to 6-methylene-bicyclo[3,l,0]heptane. A cyclobutylidene-methylenecyclopropane rearrangement of either carbene could give 1 -norcarene which could isomerize to the observed product. 

Diol (1) is used to prepare cyclopropenone acetal (2). Its highly nucleophilic double bond forms addition products with alcohols and amines and cycloaddition products with dienes to give norcarenes, ketones to give furanones and oxetanes, aldehydes to give butenolide, furan, and y-keto ester derivatives (eq 2), electrophilic alkenes to give cyclopropanes and functionalized cyclopentenones, and an a-pyrone to give a... 

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