Ketone congeners

Like their stable heavy ketone congeners, the germanetellones Tbt(R)Ge = Te underwent [2 + 3] and [2 + 4] cycloadditions with mesitonitrile oxide and 2,3-dimethyl-l, 3-butadiene, respectively144 (Scheme 39). 

Oxoepistephamiersine (14) was isolated from the roots of Stephania japonica as the seventh hasubanalactam congener (77). The UV spectrum of oxoepistephamiersine (14) showed an absorption maximum at 284 nm, and the IR spectrum exhibited bands of a six-membered ketone at 1745 cm-1 and y-lactam at 1690 cm-1. The mass spectrum (Table V) revealed the most abundant ion peak at m/z 257, indicating stephamiersine-type cleavage (13). Since oxoepistephamiersine was identical to the y-lactam (14) derived from permanganate oxidation of epistephamiersine (77), structure 14 was proposed for oxoepistephamiersine (77). 

Biomimetic reactions should also be considered for the preparation of optically active cyanohydrins (using a cyclic dipeptide as catalyst) and also for the epoxidation of a, (3-unsaturated ketones (using polyleucine or congener as a catalyst). 

Alternatively, l-oxo-l,2,3,4-tetrahydroquinolizinium ion (111 Scheme 73) and its congeners may be converted to derivatives of 1-hydroxyquinolizinium ion (63JCS2203). The bicyclic ketone (111) can be brominated to yield the 2-bromo (112) or the 2,2-dibromo derivative (113). Action of boiling acetic anhydride converts the monobromo ketone (112) to 2-bromoquinolizinium bromide (Table 2). If the same bromo ketone (112) is heated with ion-exchange resin (Amberlite IRA-400) loaded with hydroxyl ions or, alternatively, heated with silver acetate in water, the 1,2-dihydroxyquinolizinium ion is formed and may be recovered as the picrate (Scheme 74). 

The cyclodehydration method used for the synthesis of benzo[a jquinolizinium ion and its congeners (Scheme 97) requires that phenylpyridines (176) (including benzo analogs) be converted into quaternary salts (177) by the action of a -halo ketones or a -halo aldehyde derivatives. The acid-catalyzed cyclization of these salts (177) has provided access to a number of compounds containing the benzo[a]quinolizinium system (178) (Table 8). 

The first report of the preparation of the dialkyl succinimide (29-3) dates back to early in the twentieth cenmry. It is consequently surprising to note that it was introduced as an anticonvulsant, under the name ethosuximide, well after its more recently synthesized congeners. The synthetic route starting from methyl ethyl ketone generally follows that above with the exception of the use of ammonia in the last step. The compound thus differs as well by possessing a somewhat acidic imide proton [30]. 

Miyashita, M. Suzuki, T. Hoshino, M. Yoshi-koshi, A. The organoselenium-mediated reduction of a,fl-epoxy ketones, a,fl-epoxy esters, and their congeners to /J-hydroxy carbonyl compounds novel methodologies for the synthesis of aldols and their analogs. Tetrahedron 1997, 53, 12469-12486. 

Within the Lymantriidae, patterns of pheromone use are not yet clear, and there appears to be the greatest diversity of pheromone structures. Roughly two-thirds of the approximately thirty species for which pheromones or sex attractants have been reported have polyenes, epoxides, ketones, or polyunsaturated esters that could be classified as belonging to the Type n class, whereas the remainder use branched-chain epoxyalkane pheromones. Remarkably, even within a genus (e.g., Lymantria or Euproctis), congeners produce pheromones of different classes (Table 18.4). 

Carbonyl compounds such as ketones and aldehydes are another important class of doubly bonded systems in organic chemistry. However, their heavier element congeners, heavy ketones , are much less explored because of the extremely high reactivities. 

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