586. Photochemical cyclisation of diels–alder adducts

This paper is dedicated to Professor Ross Stewart on the occasion of his 65th birthday PETER YATES and KRZYSZTOF SWITLAK. Can. J. Chem. 68, 1894Chem. 68, (1990.The exo-cis isomer (8) of the well-known endo-cis 1: 1 adduct (4) of cyclopentadiene andp-benzoquinone has been obtained by heating the endo-cis-anti-cis-endo 2: 1 adduct (13) withp-benzoquinone and also by heating 4 alone. The exo-cis isomer of the 1 : 1 adduct (11) of cyclopentadiene and p-toluquinone has also been obtained for the first time. Heating of the 2: 1 adduct 13 gives a mixture containing the endo-anti-e.ro isomer 15, the exo-anti-e.ro isomer 16, and 13. The structures of these two new isomers are assigned on the basis of (i) spectroscopic comparison with 13 and the known endo-syn-endo and endo-syn-exo isomers, 12 and 14; (ii) spectroscopic comparison of the corresponding tetrahydro compounds; and (iii) the conversion of tetrahydro 15 by oxidation and acetylation to the syrz-hydroquinone diacetate 28, which is stereoisomeric with the anti-hydroquinone diacetate 25, prepared by similar treatment of tetrahydro 13, 14, and 16. It is proposed that interconversion of the 1:l adducts occurs via dissociation-recombination, interconversion of the tetrahydro 2: 1 adducts occurs via enolization, while interconversion of the 2:l adducts themselves can occur by both routes.

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confidence: 99%

“…Tetrahydro 2:l adducts Hydrogenation of the original 2: 1 adduct 13 gives a tetrahydro compound 23, mp 255°C; similar treatment of the isomer 1 4 gives a tetrahydro compound 24, mp 188°C (13,15,16). Compound 24 could also be obtained by alkaline treatment of 23 in :he same fashion that 13 was converted to 14, or by heating 23 above its melting point (ca.…”

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confidence: 99%

The 1:1 and 2:1 adducts of cyclopentadiene with p-benzoquinone

Yates¹,

Switlak²

1990

“…The equilibrium 12 13 evidently lies far to the right (no C=O bond in ir spectrum). By contrast, Cookson et al (4) found that treatment of 1 with one mol (4 equivalents) of sodium borohydride gave a mixture of mono-and di-reduction products, and that the former existed mainly as uncyclized hydroxy ketone (C=O in ir). Treatment of 1 with a large excess of borohydride gave a mixture of isomeric diols.…”

Section: "Ohmentioning

confidence: 99%

“…gave the ether 14 as the only product, even after The attempt to obtain bishomohypostrophene prolonged standing. Recently Nakazaki et al (1 1) from the homologous diketone 9 (4,8,9) by a simi-converted 10 into 14 by treatment with sulfuric acid lar series of reactions failed. Lithium aluminum in acetic acid at 120°C for 42 h. Evidently polyhyhydride reduction of 9 gave a diol(10, 11) for which drogen fluoride -pyridine may prove advantageous Dekker et al (10) have established the endo,endo in the conversion of some diols into ethers under configuration (10) by reaction with thionyl chloride mild conditions.…”

Section: Introductionmentioning

confidence: 99%

The reaction of potassium iodide in polyhydrogen fluoride – pyridine with two cage diols. A simple synthesis of tetracyclo[6.3.0.0^4,11. 0^5,9]undeca-2,6-diene ("homohypostrophene")

Dong¹,

Edward²

1980

“…The excellent overall yields of dilactones 5 and 8 from such readily available precursors render these compounds highly accessible synthons for all- (1,6) although apparently only two of these have been reduced to their dihydro derivatives (3,4). Thus, a considerable scope of synthetic utility is predictable for this sequence.…”

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confidence: 99%

The synthesis of 2,3,5,6-endo,endo,endo,endo-tetrakis-substituted bicyclo[2.2.1]heptanes

Butler¹,

Munshaw²

1981

. Can. J. Chem. 59, 3365 (1981). Oxidation of the readily available diketone 2 affords high yields of the symmetrical dilactone 5, from which the all-endotetrakis(hydroxymethy1)norbornane 10 can be made. A related tetrol22 is also described. These tetrols are dehydrated to polycyclic di-ethers 12, 13, and 23 which constrain their oxygen atoms in rigid proximity within their structures. DOUGLAS N. BUTLER et TIMOTHY J. MUNSHAW. Can. J. Chem. 59,3365 (1981). L'oxydation de dicetone 2. que I'on peut obtenir facilement conduit avec d'excellents rendements a la dilactone symetrique 5 a partir de laquelle on peut preparer !e tetrakis (hydroxymethy!) norbonanes (10) completement endo. On decrit egalement le tetrol apparente (22). La deshydratation de tetrols conduit aux diethers polycycliques 12.13 et 23 dans lesquels les atomes d'oxygene sont maintenus dans un voisinage rigide a I'interieur de leurs structures.[Traduit par lc journal]The anticipated congestion of the endo face requires that any scheme directed toward the preparation of a 2,3,5,6-all-endo-tetrasubstituted norbornane must mark the prevention of epimerization of one (or more) of the substituents of any of the intermediates of the synthesis into the more stable exo stereochemistry. The caveat is successfully countered by using the readily available photo-cage 1 (1) from the cyclopentadienelbenzoquinone Diels-Alder adduct as the starting point of the synthesis only if the necessary carbon-carbon disconnections within 1 can be effected by processes which exclude any possibility of such an isomerization, preferably intramolecular events which maintain the all-endo stereochemistries until nonepimerizable functionalities are in place.A 2,3,5,6-tetrakis(hydroxymethy1) derivative of norbornane has been described (2), the origins of which suggest 2,3-endo,endo-5,6-exo,exo as the likely stereochemistry. The objective of this work was to prepare the all-endo isomer in order to study the chemical and physical consequences of the congestion imposed on the functionalities by this geometry. The dissolving-metal reduction (3) of the cage dione 1 required refluxing conditions (4) in our hands in order to produce 2. Curiously, very little chemistry has been described for this diketone, although it is easily prepared and ideal for the purpose at hand. Initially, we envisioned functionalizing the two methylene carbons a to the carbonyls as a logical strategy; however, selenium dioxide oxidation to the anticipated tetraketone 3 failed. A stereospecific bromination proceeded very efficiently to give a dibromide to which we ascribe the structure 4 from steric and spectroscopic rationalizations. The acetate and hydroxide anionic nuclieophiles did not change 4 under the conditions tried and a stronger base (methoxide) slowly produce a rearranged monobromoketo-ester of unknown structure (presumably via a Favorskii mechanism).Although unreactive to m-chloroperbenzoic acid, 2 reacted cleanly with trifluoroperacetic acid at room temperature to produce a mixture of dilactones. Fortuna...