Ketones, polycyclic

Various organic molecules are used as photosensitizers in liquid-phase reactions, for example, anthraquinones, aryl ketones, polycyclic aromatic hydrocarbons, dyes, etc. The following mechanism, as the most probable, was suggested for the initiation by the organic photosensitizer Q with the aromatic ring [204-208] ... 

Gel permeation chromatography Phenols, phthalate esters, nitrosamines, organochlorine pesticides, PCBs, nitroaromatics, cyclic ketones, polycyclic aromatic hydrocarbons, chlorinated hydrocarbons, organophos-phorus pesticides, priority pollutant semivolatiles... 

Treatment of 210 under traditional Eschenmoser fragmentation conditions gave only low yields of the desired alkynyl ketone 211, but this result was improved significantly by use of p-nitrobenzenesulfonylhydrazine in place of the commonly used p- lolueriesul fonylhydrazine. Compound 211 was transformed into the bis-oxime 212, reductive cyclization of which by treatment with ZrCU and NaBH4 and subsequent acylation afforded the polycyclic compound 213 with the desired all-cis... 

An interesting family of polycyclic pyrroles was described in 2005 using again the synthetic sequence of a Stetter reaction for the preparation of the starting 1,4 diketones followed by a microwave-assisted Paal-Knorr condensation [35]. For example, cyclopentenone 23 (obtained in a Pauson-Khand cyclization) reacted imder Stetter reaction conditions to give the amino ketone 25 (Scheme 8). The microwave-assisted Paal-Knorr cyclization of 25 with different amines gave a small collection of tricychc pyrrole 2-carbox-amides. 

The Pictet-Spengler reaction has mainly been investigated as a potential source of polycyclic heterocycles for combinatorial apphcations or in natural product synthesis [149]. Tryptophan or differently substituted tryptamines are the preferred substrates in a cyclocondensation that involves also aldehydes or activated ketones in the presence of an acid catalyst. Several versions of microwave-assisted Pictet-Spengler reactions have been reported in the hter-ature. Microwave irradiation allowed the use of mild Lewis acid catalysts such as Sc(OTf)3 in the reaction of tryptophan methyl esters 234 with different substituted aldehydes (aliphatic or aromatic) [150]. Under these conditions the reaction was carried out in a one-pot process without initial formation of the imine (Scheme 86). 

REARRANGEMENT OF BRIDGEHEAD ALCOHOLS TO POLYCYCLIC KETONES BY FRAGMENTATION-CYCLIZATION 4-PROTOADAMANTANONE... 

The procedure described here is a modification of one involving the thermal fragmentation of 1-adamantyl hypoiodite and cycliza-tion of the resulting iodo ketone/ By means of this procedure, 4-protoadamantanone is obtained from 1-adamantanol with consistent yields in the range of 71 to 82% and a purity greater than 98%. This method is also applicable to the preparation of other polycyclic ketones from the related bridgehead alcohols with a-bridges of zero, one, or two carbon atoms (see Table I). 

Anhydride (1), used to make polycyclic ketones, and diester (2), used in a study of oxidative decarboxylation,have each been made in one step by Diels-Aldcr reactions. 

Energetically rich polynitro compounds have been prepared from polycyclic ketones by the conversion of oximes to nitro compounds, as shown in Table 2.6. 

Our work on the bifunctional activation of CO insertion was prompted by the thought that strong molecular Lewis acids should be more effective and more general than simple cations. It already had been observed that molecular Lewis acids would promote a molecular Fischer-Tropsch type reaction (5), and that iron diene complexes can be converted to polycyclic ketones by the action of aluminum halides, equation 7,(18), but information on the course of these reactions was sketchy. 

On treatment with a base such as NaOMe or even LLAIH4, mono-cycloadducts of mesitonitrile oxide and polycyclic aromatic hydrocarbons have been cleaved to yield the corresponding oximes, which are oxidized to ketones by the Dess— Martin method. The same ketones have been obtained by reductive ring opening of the mono-cycloadducts with Raney Ni (438). 

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