The bicyclic ketones 1-6 entered into diastereoselective (> 95% d.e.) aldol reactions with a variety of aldehydes (Scheme 1 and Table 1). A representative series of aldols was converted (E)-selectively into alpha,beta-unsaturated ketones by i) spontaneous base-promoted dehydration (Scheme 1 and Table 2) and also by ii) conversion into brosylate and base-mediated elimination with lithium diisopropylamide/N,N,N',N'-tetramethylethylenediamine (LDA/TMEDA; Scheme 2). The simple alpha-methylidene ketones 17a and 18a were obtained via oxidation of the phenylselenides 19 and 20, respectively (Scheme 4). The tertiary aldol 27 was synthesized best by treatment of 1,3-diketone 26 with Me4Zr (Table 4). In this fashion, the facile retro-aldol reaction of 27 was suppressed effectively.

Nonenolizable 6-hydroxy-2,4-cycloheptadien-1-ones, including spiro[4.6] and spiro[5.6] annulated derivatives, have been prepared and shown to rearrange intramolecularly into 5-cyclohepten-1,3-diones at room temperature and even at −18°C. The rearrangement is accelerated in solvent DMSO.

8-Oxabicyclo[3.2.1]oct-6-en-3-ones 3 with a quaternary centre adjacent to the carbonyl group have been converted into 6-hydroxy-2,4-cycloheptadien-1-ones 1 with zirconium tetrachloride/piperidine (1:1).

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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.