5011-61-0Relevant articles and documents
Ring strain release as a strategy to enable the singlet state photodecarbonylation of crystalline 1,4-cyclobutanediones
Kuzmanich, Gregory,Garcia-Garibay, Miguel A.
supporting information; experimental part, p. 883 - 888 (2012/01/13)
Challenging most chemists' intuition, highly reactive dialkyl biradicals can be reliably generated in the solid state by taking advantage of the photodecarbonylation of cyclic ketones. However, it has been shown that radical stabilizing groups with resonance-delocalizing abilities at the α-carbons of the precursor are required to facilitate the α-cleavage reaction, and that triplet state reactivity is essential to slow down the combination of the intermediate acyl-alkyl biradical back to the starting ketone. Relatively long triplet acyl-alkyl biradical lifetimes give a chance for the loss of CO to occur. Looking for additional strategies to generate transient biradicals in solids, we studied the solid state photochemistry of four aliphatic, dispiro-substituted 1,4-cyclobutandiones (1a-d) that were expected to react from the singlet state. We hypothesized that the release of ring strain from the small ring carbonyl would make the reverse acyl-alkyl combination disfavored, allowing for the loss of CO to occur efficiently and irreversibly. We report here the results of studies carried out in solution, bulk (powder) crystals, and nanocrystalline photochemistry. We have recently shown that excitation of dispirocyclohexyl-1,3-cyclobutanedione 1c led to the trapping of the intermediate oxyallyl with a half life of about 42 min. Our studies with the three other crystalline derivatives revealed that, while all react efficiently, the remarkably long lifetime of oxyallyl is unique to crystals of 1c.
Addition Reactions of Heterocyclic Compounds. Part 80. Dimethyl Acetylenedicarboxylate with 4,5,8,9,10,11-Hexahydro-7H-cycloheptapyrroloindole and 4,5,7,8,9,10,11,12-octahydrocyclooctapyrroloindole
Letcher, Roy M.,Choi, Michael C. K.,Acheson, R. Morrin
, p. 1634 - 1672 (2007/10/02)
The reactions of dimethyl acetylenedicarboxylate with pyrroloindoles which have either a penta- or hexa-methylene chain linking positions 2 and 3, have been found to give rise to somewhat similar arrays of products.Thirteen new adducts were isolated and their structures established by 1H and 13C n.m.r. spectroscopy, and in some cases by chemical transformations.Their structures reveal four new classes of adducts which are either substituted indoles, or adducts formed via the ring opened amino-ketones; two of the new adduct types are formed via novel skeletal rearrangements.An unusual acetic acid catalysed dehydrogenation was also observed for the (1 + 2 DMAD - CH4O) adducts.Both indoles hydrolyse in sulphuric acid to give the corresponding amino-ketones, the reactions of which were investigated.
Addition Reactions ofHeterocyclic Compounds. Part 79. Reaction of Dimethyl Acetylenedicarboxylate with some Cycloheptindoles and Cyclo-octindoles
Letcher, Roy M.,Choi, Michael C.K.,Acheson, R.Morrin
, p. 515 - 526 (2007/10/02)
The reactions of dimethyl acetylenedicarboxylate with N-methyl- and pyridoindoles which have either a penta- or hexa-methylene chain linking positions 2 and 3, have been found to give rise to a very similar array of products.Nineteen new adducts were isolated and their structures established by 1H and 13C n.m.r. spectral comparisons, and in some cases also by chemical transformations.The structures include five new classes of adducts not previously encountered: two types of (1+1 DMAD) adducts, one of which is a cyclobutene and the other a 3-maleate; two types of (1+2 DMAD) adducts, one with two side chains, and the other having a ring-expanded nine- or ten membered ring and one side chain; and a (1+2 DMAD - CH4O) adduct, all examples of which exhibit fragmentation on heating to give a carbazole and a spiro-cycloalkyl-keten dimer.The isolation of the two (1+1 DMAD) adducts is important as both adduct types have been postulated as intermediates in the formation of more complex adducts.
