Pentaprismane synthesis

The Baeyer-Villiger oxidation has been utilized as an element of several novel functional group manipulations. Suginome and Yamada converted adamantanone (64) to 2-thiaadamantane (66) via the lactone (65 Scheme 19). Eaton et al.P in the synthesis of pentaprismane (70) from homopentaprismanone (67 Scheme 20), required that a leaving groiq) be introduced a to the carbonyl group in or r to carry out a Favorskii ring contraction. Oxidation of (67) afforded lactone (68), which was converted in several steps to the requisite hydroxy ketone (69). 

The Favorskii rearrangment was also successfully used as the key step in the synthesis of pentaprismane 359, and numerous other cases. 

Photodimerization of the dihydronicotinamide (101) yields the cis,syn,-cis-dimer (102). Subsequent irradiation of this yields the cage compound (103). Cage compound formation has also been reported as result of the photochemical ring closure of the adduct (104) this reaction proceeds efficiently to yield (105), which was used as a key intermediate in the synthesis of pentaprismane (106), The cage compounds (107) have been synthesized by... 

Diazabicyclo[2.2.2]oct-2-enes have been shown to undergo photoelimination of nitrogen in a similar fashion via singlet 1,4-biradicals.In a separate investigation, the azoalkane (32) was converted into the bicyclo[2.2.0]hexane (33) in 72% yield on irradiation, and an analogous transformation has been employed in the synthesis of compounds with a pentaprismane carbon skeleton. ... 

A classical method using Na- or Li-liquid ammonia (Birch reduction conditions) is effective for reductive dehalogenations of aryl and vinylic halides, but it is not always successfully applied to alkyl halides, although cyclopropyl halides and bridgehead halogens are exceptions.Under such conditions, the reactions are often accompanied by side reactions, such as elimination, the Wurtz coupling reaction, cyclization and reduction of carbonyl compounds. An example, a synthesis of pentaprismane (1), is shown in Scheme 4. ... 

Pentaprismane was first made by Eaton, Or and Branca in 1981 [13]. The synthesis is more involved than that of cubane (which was more involved than that of prismane) because a prismane-type approach (extrasion of dinitrogen from the azo compoimds 12 or 13) fails, and a cubane-type photocyclization approach ([2+2] cycloaddition with 14) did not work on 14 ... 

Let us close this account of simple prismanes with a look at hexaprismane. The synthesis of cubane was reported in 1964 pentaprismane was said (1974) to show extraordinary synthetic inaccessibility [16], but was made in 1981 [13] and hexaprismane has so far (early 2007) resisted all attempts at synthesis [5]. As Hopf points out [5], hexaprismane can in principle be assembled from two benzene rings or from cyclobutadiene and cyclooctatetraene ... 

Pentaprismane represents the last of the prismanes that have been prepared, whether by a quasi-Favorskii rearrangement or other means. Eaton et al. reported the synthesis in 1981. ... 

Extremely highly strained C-C framework compounds such as cyclopropane, tetrahedrane, cubane and prismane have been synthetic targets among organic chemists for a long time. Cyclopropane, tetrahedrane and cubane are highly symmetric compounds with three-fold axes. In 1964, Eaton and Cole performed the first synthesis of cubane. " In 1973, Kats and Acton reported the first production of prismane. In 1981, Eaton et al. reported the first production of pentaprismane. In 1978, Maier et al. successfully isolated tetrahedrane with three-fold tert-butyl substituents by photolysis of the corresponding 2-cyclopentadienone derivative. Tetrahedrane is an isomer of cyclobutadiene. 

The Favorskii rearrangement has frequently been employed in ring contractions. For example, a Favorskii ring contraction was employed in the synthesis of the cage compound 12 en route to a hexacyclotetradecane, and of cage compound 14 en route to pentaprismane. ... 

The abiotic evolution of container-type molecules may be traced from the original synthesis of cubane [94], pentaprismane [95], and dodecahedrane [96]. 

SCHEME 3 Synthesis of [S] prismane (pentaprismane). (From Reference 4.)... 

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