The chemistry of alkyne cyclooligomers dates back to the 18th century with the work of Berthelot1 and Kekulé;2 however, the first dimeric species, namely the cyclobutadienes, were only reported in 1959 as an ?/4-complex3a b and in 1968 as a free, not complexed molecule with a push-pull substitution pattern.30•4 Much more recently, the chemistry of the related A3-phosphaalkyne (A) cyclooligomers has attracted considerable attention.5 A few dimers are stable in the coordination sphere of transition metals,5•6 but free lA3,3A3-diphosphetes B and 1A3,2A3diphosphetes C behave as their antiaromatic carbon analogs and prove to be elusive.5•7 In the same vein, only one example of transition metal-coordinated A3-phosphete D,8 arising from the inner sphere codimerization of alkynes with A3-phosphaalkynes A, is known. In marked contrast, although a very few A5-phosphaalkynes E are stable,9 most of them spontaneously dimerize, leading to stable lA5,3A5-diphosphetes F.10 Here we report the first example of codimerization of a A3-phosphaalkyne A with a A5-phosphaalkyne E (Chart 1).In contrast to most diazo derivatives,5b 0 bis[diisopropylamino)phosphino](trimethylsilyl)diazomethane (1) does not undergo

heterocyclic 4-membered rings heterocyclic 4-membered rings R 0055 -151Antiaromatic Compounds. Part 30. The Reactivity of a Kinetically Stabilized Azete Towards Mesoionic Compounds.-Different products are formed depending on the educt used. Additionally, it is shown that photolysis of the triazepines (III) gives the pyrazoles (V) and pyrolysis of azetes of type (VIII) as well as (VII) leads to pyrroles. -(BACH, P.; BERGSTRAESSER, U.; LEININGER, S.; REGITZ, M.; Bull. Soc. Chim. Fr.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Tropone (11, with its 8n-electron system, and the kinetically stabilized phosphaalkynes 3a-c undergo cycloaddition reactions, in dependence on the stoichiometry and reaction conditions, to furnish co-oligomeric phosphorus-carbon cage compounds 5a,b or 9a-c, respectively. When tropone (1) is subjected to thermolysis conditions in the presence of a n excess of the phosphaalkyne 3a o r b but in the absence of a solvent, the homo-Diels-Alder adducts Sa o r b are isolated in 21% or 23% yield, respectively. The peri-and regioselectivities observed for this two-step reaction sequence can be precisely defined on the basis of semiempirical MO calculations (frontier orbital theory, PM3). On the other hand, when tropone (1) is heated with equimolar amounts of the phosphaalkynes 3a-c in toluene, the pentacyclic compounds 9a-c are formed in 51-64% yields as subsequent products of the [8 + 21 cycloaddition of tropone with the tetracyclic species 5a-c.Diels-Alder or, respectively, 1 ,&dipolar cycloaddition reactions of the tetracyclic species 5a with 2,3-dimethylbutadiene or mesitylnitrile oxide give rise to polycyclic products with differing skeletons (11 or 13 and 15, respectively). An X-ray crystal structure analysis of the cage compound 9a has been performed. Contribution to Organophosphorus Compounds. 101. For Part 100 see: Regitz, M.; Bergstrasser, U.; Hoffmann, A. Chem. Rev., in press.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.