ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The photochemistry of the conjugated cyclohexenones O-acetyl testosterone (1) and 10-methyl-Δ1,9-octalone-(2) (24) has been investigated in detail. The choice of reaction paths of both ketones depends strongly on the solvent used. In t-butanol, a photostationary equilibrium 1 ⇄ 3 is reached which is depleted solely by the parallel rearrangement 1 → 5 (Chart 1; for earlier results on these reactions see [2a] [6] [7]). In benzene, double bond shift 1 → 16 (Chart 3) occurs instead, which is due to hydrogen abstraction from a ground-state ketone by the oxygen of an excited ketone as the primary photochemical process. In toluene, the major reaction is solvent incorporation (1 → 17, Chart 4) through hydrogen addition to the β-carbon of the enone, accompanied by double bond shift and formation of saturated dihydroketone as the minor reactions. Contrary in part to an earlier report [19], the photochemical transformation of the bicyclic enoné 24 exhibit a similar solvent dependence. The corresponding products 25-29 are summarized in Chart 5 and Table 1.Sensitization and quenching experiments established the triplet nature of the above reactions of 1 and 24. Based on STERN-VOLMER analyses of the quenching data (cf. Figures 2, 4-8, and Table 3), rearrangement, double bond reduction and toluene addition are attributed to one triplet state of the enones which is assigned tentatively as 3(π, π*) state, and the double bond shift is attributed to another triplet assigned as 3(n, π*) state (cf. Figure 9).The stereospecific rearrangement of the 1α-deuterated ketone 2 to the 4β-deuterio isomer 4 shows the reaction to proceed with retention at C-1 and inversion at C-10.The 4-substituted testosterone derivatives 33-36 (Chart 8) were found to be much less reactive in general than 1. In particular, 4-methyl ketone 33 remains essentially unchanged on irradiation in t-butanol, benzene and toluene.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19690520414
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