Endo-peroxide group

This group is prepared by the reaction of the anion of 9-hydroxyanthracene and the tosylate of an alcohol. Since the formation of this group requires an S 2 displacement on the alcohol to be protected, it is best suited for primaiy alcohols. It is cleaved by a novel singlet oxygen reaction followed by reduction of the endo-peroxide with hydrogen and Raney nickel. 

With endo-peroxides obtained similarly in the presence of tetraphenylporphyrin from 2-methoxy-3-carbomethoxy-5-arylfurans 202, when the aryl group is electron donating (para-anisyl, p-An), the product 206 is derived from a dioxirane 205 formed by the isomerization of the intermediate carbonyl oxide (Scheme 68). With methanol a hydroperoxide 207 is obtained as in the previous case <1994JCS(P1)147>. 

The antimalarial arteminisin(130) contains an endo cyclic peroxide group, a functional group which rarely appears in natural products. 

Doubtless attempts will now be made to prepare more sophisticated model compounds that more closely resemble the natural prostaglandin endoperoxides. Thus the influence of endo-5-allyl and/or cxo-6-vinyl groups upon the chemistry of the [2.2.1] system is clearly of interest. However, it seems likely that the next major effort in this area will involve a thorough and systematic investigation of the reactions of the first generation of bicyclic peroxides that has now been obtained. 

In the case of the thermolysis of uns5mrmetrical diacyl peroxides, R—CO—O2 —CO—Ar, with negatively substituted phenyl groups e.g. Ar = 3-chlorophenyl), there is a moderate increase in reaction rate with increasing solvent polarity. They are generally considered to involve ion-pair intermediates e.g. R 02C—Ar), formed via dipolar activated complexes. A typical example is that of endo- and evo-(2-norbomyl)formyl 3-chlorobenzoyl peroxide /ri(CH3CN)/A i (cyclohexane) = 320 for the exu-reactant [563]. 

Zard has developed the use of N-amidyl radicals. The precursors of the radical intermediates are 0-benzoyl hydroxyamines such as 37. Addition of a tributylstannyl radical to the carbonyl group of the benzoate moiety is followed by the cleavage of the weak N - O bond. A subsequent 5-exol6-endo tandem cyclization takes place to yield the skeleton of the natural product deoxyserratine (Scheme 12) [49]. Later, the same group disclosed a tin-free source of amidyl radicals that relies on the use of M-(0-ethyl thiocarbonyl-sulfanyl) amides and lauryl peroxide as initiator. Examples of polycyclization were also given [50]. On the occasion of a model study toward the synthesis of kirkine, the use of thiosemicarbazide precursors gave access to the tetracyclic structure of the natural product [51]. 

Azoisobutyronitrile Cyclopropylmethyl 3-exo Cyclisation A-endo Cyclisation Collidine DEPO Diethylphosphine oxide DPT Density functional theory DTBP Di-tert-butyl peroxide EPHP AT-Ethylpiperidine hypophosphite PCI Functional group interconversions EiMPA Hexamethylphosphoramide EDA Lithium diisopropylamide MAP 4-Methoxyacetophenone PTOC AT-Hydroxypyridine thione TMM Trimethylenemethane trityl Triphenylmethyl... 

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