19037-72-0Relevant articles and documents
Free Radical Fragmentation of Photoadduct Derivatives. Formal Synthesis of Pentalenene
Lange, Gordon L.,Gottardo, Christine
, p. 2183 - 2187 (1995)
A series of photoadducts 3a-d are converted to cyclobutylcarbinyl iodides 6a-d.Free radical fragmentation of the iodides yields bicyclo carbon skeletons 7a-d which are present in a variety of natural products.Application of this methodology to terpenoid synthesis is illustrated by the preparation of unsaturated ketone 19 in only six steps (33percent overall yield).As 19 has been converted to pentalenene (1) this constitutes a formal synthesis of the angular triquinane sesquiterpenoid.
Reactions of enaminones with 1-nitroolefins. Scope and limitations of a polyquinane synthesis
Huffman,Cooper,Miburo,Pennington
, p. 8213 - 8228 (2007/10/02)
The reaction of several 2-aminocyclohex-2-en-1-ones with cyclic nitroolefins has been explored as a possible synthetic approach to polyquinanes. 2-Pyrrolidino, 2-piperidino and 2-morpholinocyclohex-2-en-1-one react with 1-nitrocyclopentene to provide substituted triquinanes. Reactions involving 5,5-dimethyl-2-morpholinocyclohex-2-en-1-one were unseccessful as were those using 4,4-dimethyl-1-nitrocyclopentene. 5-Methyl-2-morpholinocyclohex-2-en-1-one and 1-nitrocyclopentene provide the corresponding triquinane, plus a by-product in which the amino substituent has been lost. The reactions of other selected nitroolefins have been carried out, and the products are described. The results of these reactions are rationalized in terms of an inverse electron demand Diels-Alder reaction to afford an intermediate oxazine N-oxide, which then undergoes further transformations to afford the observed products.
SYNTHESIS OF dl-PENTALENOLACTONES E AND F.
Cane,Thomas
, p. 5295 - 5303 (2007/10/12)
The methyl esters of ( plus or minus )-pentalenolactone E and F have been synthesized by a route based on the intramolecular insertion of an alpha -acylcarbene into an unactivated C-H bond to effect closure of the key fused delta -lactone ring system. Lactone reduction, deketalization, and selective acetalization of the derived lactol provided as a mixture of epimers.
Photochemistry of Alkyl Halides. 9. Geminal Dihalides
Kropp, Paul J.,Pienta, Norbert J.
, p. 2084 - 2090 (2007/10/02)
The photobehavior of the geminal dihalides (diiodomethyl)cyclohexane (7), (bromoiodomethyl)cyclohexane (11), (dibromomethyl)cyclohexane (17), (diiodomethyl)cyclopentane (22), 3,3-dimethyl(diiodomethyl)cyclobutane (27), and 8,8-diiodo-2,6-dimethyl-2-octene (31) has been studied and compared with that previously observed for diiodomethane.In all solvents the corresponding vinyl halides (iodomethylene)cyclohexane (13), (bromomethylene)cyclohexane (21), (iodomethylene)cyclopentane (23), 3,3-dimethyl(iodomethylene)cyclobutane (28), or cis- and trans-3,7-dimethyl-1-iodo-1,6-octadiene (33) were obtained, which are thought to arise from α-halo cationic intermediate formed via initial light-induced homolytic cleavage of the carbon-iodine bond followed by electron transfer within the resulting caged radical pair, as shown in Schemes II and III.In the case of diiodide 31 competing intramolecular trapping of the α-iodo cation afforded in addition the cyclized isopulegyl iodide (34).In polar solvents the vinyl iodides were accompanied by the nonhalogenated products methylenecyclohexane (15), 1-methylcyclopentene (25), cyclohexene (26), 4,4-dimethylcyclopentene (29), and cis- and trans-carane (35), which are thought also to arise from the α-halo cationic intermediate. 1.1-Diiodo-2,2-dimethylpropane (1b) afforded 2-methyl-2-butene (6b).Except for carane (35) from diiodide 31 there was no detectable formation of cyclopropanes.In methanol the nucleophilic substitution products (dimethoxymethyl)cyclohexane (14), (dimethoxymethyl)cyclopentane (24), and 1,1-dimethoxy-2,2-dimethylpropane (30) were obtained.It is concluded that geminal dihalides undergo predominant, if not exclusive, photoreaction via initial clea vage of a single carbon-halogen bond in analogy with monohalides and that carbene intermediates are not formed.A similiar conclusion has been reached previously for diiodomethane in the photocyclopropanation of alkenes.
