Fenchones, synthesis

Exercise 30-8 One route for the synthesis of D,L-fenchone is through the following steps. Show the reagents, conditions, and important reaction intermediates you expect would be successful in achieving each of the indicated transformations, noting that more than one step may be required (all the reactions necessary have been described in previous chapters). 

Figure 5.8 Synthesis of a difenchyl imidazolium salt from fenchone.

Other miscellaneous cyclization reactions leading to interesting thiophene derivatives include a thermal conversion of a 2,2 -bis(A/,Af-dimethylthiocarbamoyloxy)-1,1 -binaphthyl into a dinaphtho[2,l-6 l, 2 -t/ thiophene (a heterohelicene) <0581109>, solution-phase parallel synthesis of a 1140-member ureidothiophene earboxylic acid hbrary <05JCC253>, and an unexpected cyclization occurring upon metalation of diphenylsulfone, followed by introduction of (-)-fenchone and subsequent aqueous workup <05T10449>. Heating of the... 

A vast array of chiral auxiliaries have been derived from naturally occurring compounds containing the bicyclo[2.2.1]heptane unit (for review articles, see refs 1 -3). In all cases, the ultimate sources of these auxiliaries are the ketones camphor and fenchone, and the alcohols borneol and fenchol, as at least one enantiomer of each compound is provided in enantiomericaUy pure form by nature. Thus. ( + )-camphor [( + )-2], (-)-borneol [(-)- ], and (+)-fenchonc [( + )-5] are enan-tiomerically pure, convenient and inexpensive starting materials for organic synthesis and deriva-tization to give chiral auxiliaries. Most other compounds of this series are also commercially available, but can be prepared by oxidation or reduction of inexpensive precursors by standard methods. The evo-alcohols, such as the enantiomeric isoborneols, are accessible by standard complex hydride reductions of the ketones. The interconnection between these compounds is shown diagrammatically. 

The Martinez group has demonstrated the versatility of the Wagner-Meerwein rearrangement in the enantiospecific synthesis of C(10)-substituted camphors and fenchones from readily available (-i-)-camphor (103) and (-)-fenchone (104). These derivatives represent a multitude of substitution tjmes, including C(10)-O-, C(10)-Br-, C(10)-S-, C(10)-Se-C(10)-N-, C(10)-C-N-, and C(9,10)-dihalocamphors. They are of... 

A soln. of -butyllithium in hexane added dropwise at 0° to a soln. of 1,1-di-phenylethylene in anhydrous tetrahydrofuran, stirred 85 min. at room temp., treated with triphenylborane as hydride acceptor in tetrahydrofuran, and the product isolated after 15 hrs. -> 1,1-diphenyl-1-hexene. Y 89%. F. e. s. M. T. Reetz and D. Schinzer, Ang. Ch. 89, 46 (1977) hydride elimination also from organomagnesium compds. and f. hydride acceptors s. ibid. 89, 46 fenchone as hydride acceptor cf. Synthesis 1977, 135. 

Synthesis of Selenoketones.—Two new simple monomeric selenoketones, seleno-fenchone (24) and the blue di-t-butyl selenoketone, were prepared by heating the ketone phosphoranylidene hydrazones with selenium. Treatment of a... 

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