856. Syntheses of perhydroanthracenes involving the reduction of thioketals with lithium and ethylamine. The synthesis of 1,4,4aα,5,8,8aβ,9,9aβ,10,10aα-decahydroanthracene

Abstract

The unsaturated diketones (I) and ( 11) have been converted in good yields into the corresponding perhydroanthracencs by reduction of their bis(ethy1ene dithioketals) with lithium and ethylsmine. A diem (XIII) required for the study of its addition reactions has been synthesised. ALDER and STEIN^ first condensed P-benzoquinone with butadiene (2 mol.) to give a product that they regarded as the diketone (I) or its stereoisomer with all-&-bridgehead hydrogen atoms. We show below that this adduct has the structure (I), the second molecule of butadiene adding to the less hindered side of the bicyclic intermediate. The same conclusion has been reached by Hill and Martin for this compound, and by de Vries, Heck, Piccolini and Winstein 3 for the related adduct from $-benzoquinone and cyclopentadiene. Alder and Stein also isomerised the adduct (I) to the more stable diketone (11) under alkaline conditions, and they hydrogenated this diketone to the saturated diketone (111).The primary objective in our work in this series was the synthesis of the diene (XIII), containing parallel double bonds and with the same stereochemistry as diketone (11) The synthesis of the diene is given below, but an approach involving the removal of carbonyl groups from the diketone (11) by the intermediate formation and reduction of a bisdithioketal was also attempted. The bis(ethy1ene dithioketal) (V) was formed from the diketone (11) and ethanedithiol in high yield by using boron trifluoride as catalyst. Desulphurisation of the thioketal by Raney nickel was slow,* and reduction was attempted b y lithium and e t h ~l a m i n e . ~. ~The reduction of the thioketal was not, however, appreciably faster than that of the olefinic bonds for, after complete removal of sulphur from the molecule, the known, saturated perhydroanthracene (VIII), m. p. go", was obtained. This structure is established by X-ray diffraction methods6The lithioethylamine technique is a new and effective way for reducing thioketals and the perhydro-compound (VIII) was also obtained by reduction of the thioketal (VI) from the saturated diketone (111). The procedure should not affect the stereochemistry of the bridgehead positions; preparation and reduction of the thioketal of the initial benzoquinone-butadiene adduct gave a perhydroanthracene, m. p. 121". The following arguments indicate that this hydrocarbon has structure (VII), the original adduct therefore having structure (I). The hydrocarbon (VII) should exist in a relatively strainless threechair-conformation. Nevertheless, as it contains two axial carbon substituents on the * Hill and Martin report the reduction of this thioketal to the saturated hydrocarbon in unstated yield by Raney nickel in boiling ethanol.

Studies of the Cis, Cis‐Cyclodeca‐1,6‐Diene System

“…We also tried to reduce VII with sodium in liquid ammonia [10] and tosylhydrazone XXI with LiAIH 4 [II]. Both these compounds yielded XIX as the sole product in a 30-35% yield.…”

“…We tried to prepare the [10] annulene quinone (XXIX) [2a, 18]. Reaction of IV with one equivalent of perbenzoic acid yielded the Bayer-Villiger oxidation product, i.e., the keto-lactone XXXI, instead of the monoepoxy diketone XXX (Chart 3).…”

“…1,6-Bisdehydro [10] annulene (I) [I] is an example of a cyclodecapentaene skeleton without the internal interference caused by the two hydrogen atoms in the 1,6positions present in II [2]. II III a, X=CH 2 b,X=O c, X=S Cyclodeca-l,6-diyne (IlIa) and its derivatives, which could be the appropriate starting compounds for this system, have been synthesized only recently [3].…”

The Isomerization of 7,14-Diketo-1,2,3,4,6,6a,7a,8,8a,9,10,11,13,13a,14a,14b- hexadecahydrodibenz[a,h]anthracene

“…Isomerization of the cis-anti-cis isomer of the butadiene-p-benzoquinone bisadduct with alkali6 is known to yield the trans-syn-trans isomer. 4 It cannot be concluded from this that the isobisadduct lb of the present study has the same configuration. However, a comparison of the melting points in the hydroanthraquinone and hydrodibenz [a,/i]anthraquinone series and their hydrogenation products is of interest.…”

Desulfurization of Thioketals into Methylene and Methyl Derivatives: Nickel or not Nickel?

“…Crossley and Henbest reported that Li/liquid ammonia can be replaced by Li/EtNH 2 for the electron‐mediated desulfurization of thioketals of perhydroanthracenes . This protocol produced the methylene compounds in good yields did not affect the stereochemistry of the bridge head positions.…”