Spirocydic compound

Hasegawa et al. [85] have explored the electron transfer-promoted regioselective ring opening of cyclopropyl silyl ethers 183 for the generation of cyclopropoxy radical 185 which, upon intramolecular radical cyclization, leads to the formation of spirocydic compound 184 in moderate yields (Scheme 8.51). 

A second form of optical isomerism analogous to that shown by organic spirocydic compounds has been demonstrated. Any molecule will be optically active if it is not superimposable on its mirror image. The two enantiomers of bis(ben-zoylacetonato)beryllium are illustrated in Fig. 12.3. In order for the complex to be chiral, the chelating ligand must be unsymmetric (no/ necessarily asymmetric or chiral, itself) [Be(acac)2] is not chiral. 

The reaction proceeds via a spirocydic ii-allyl intermediate. Diethyl malonate and dicyanomethane were used as the precursors to stabilized carbanion carbon nucleophiles. In one example, the spirocydic compound 25 was obtained from 19 in 60% yield (Eq. (11.22)). 

In 2013, Kotha and coworkers [17] reported a diversity-oriented approach to novel spirocydic compounds via this process using CpCofCOlj as the catalyst. This reaction afforded the dimer as a minor side product. 

Stockman and coworkers [329] developed a straightforward synthesis of a tricyclic compound 2-636 which has some resemblance to the spirocydic portion of the natural product halichlorine (2-637) [330], On treatment of the symmetrical ketone 2-633, accessible in five steps from alcohol 2-632, with hydroxylamine hydrochloride the spiro piperidine 2-636 could be obtained in 62% yield (Scheme... 

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