Photochemistry of unsaturated ketones in solutions. XXVII. Synthesis and photochemistry of .DELTA.1-4-alkyltestosterones

Schuster, David I.; Barringer, William C.

doi:10.1021/ja00732a030

Cited by 9 publications

(4 citation statements)

References 3 publications

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“…The reaction occurs with a low to moderate quantum yield and is somewhat more efficient in 2-propanol, possibly due to the increased energy of the nπ* triplet. With simpler cyclohexadienone models quantum yields are larger than observed here (0.75 to 1),14a and this holds also for the strictly related Δ 1 -dehydrotestosterone, where the rearrangement quantum yield is 0.58, though the value is lower with some 4-alkyl derivatives 14b. Thus, the low Φ r with the present steroidal ketones is probably linked to the fluorine substitution.…”

Section: Discussionsupporting

confidence: 46%

Noncommunicating Photoreaction Paths in Some Pregna-1,4-diene-3,20-diones

et al. 2001

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The photochemistry of three pregna-1,4-diene-3,20-diones bearing a hydroxy or alkoxy group at C(17) (4-6) has been examined. Irradiation at 254 or 366 nm, where absorption by the cross-conjugated ketone moiety in ring A is predominant or exclusive, causes the 'lumiketone' rearrangement of this chromophore in low to medium quantum yield (Phi(r) 0.05 to 0.31). On the contrary, irradiation at 310 nm, where the isolated ketone at C(20) absorbs a large portion of light causes Norrish-I fragmentation of that chromophore with a higher Phi(r) (0.11-0.83). This leads to end-products arising from the conversion of the C(17) alkyl radical, in a way depending on the structure and the medium (reduction by hydrogen donating solvent, addition of oxygen when present). No intramolecular T-T energy transfer between the separated chromophores occurs. The 'lumiketone' rearrangement occurs independently from the irradiation wavelength (Phi(r) 0.06-0.18) with the strictly related androsta-1,4-dien-3-one 8 lacking the C(20) ketone function.

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Section: Discussionsupporting

confidence: 46%

Noncommunicating Photoreaction Paths in Some Pregna-1,4-diene-3,20-diones

et al. 2001

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“…On monocyclic cyclohexa-2,5-dienones, it occurs with quantum yields close to unitary (0.75−1), although it has been reported that some substituents affect the efficiency of the photoprocess, a fact mainly attributed to a change in the stability of the suggested zwitterionic intermediates of the rearrangement. − In polycyclic derivatives, and in particular with steroid cyclohexadienones, the quantum yield is slightly lower. A value of 0.58 has been reported for Δ 1 -dehydrotestosterone, a compound strictly related to the presently studied ketones.…”

Section: Discussionmentioning

confidence: 75%

“…[8][9][10] In polycyclic derivatives, and in particular with steroid cyclohexadienones, the quantum yield is slightly lower. A value of 0.58 has been reported for ∆ 1 -dehydrotestosterone, 11 a compound strictly related to the presently studied ketones.…”

Section: Discussionmentioning

confidence: 75%

General Patterns in the Photochemistry of Pregna-1,4-dien-3,20-diones

et al. 2003

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The photochemistry of six pregna-1,4-dien-3,20-diones has been compared and found to involve both the cyclohexadienone moiety in ring A and the isolated ketone at C-20. The two reactions take place proportionally to the fraction of light absorbed by each chromophore. The cross-conjugated ketone absorbs predominantly or exclusively at both 254 and 366 nm and undergoes the "lumi" rearrangement to bicyclo[3.1.0]hex-3-en-2-one. The quantum yield of the reaction diminished somewhat with increasing lambda(exc), e.g., for prednisolone Phi(254) (nm) = 0.42, Phi(366) (nm) = 0.3. A much stronger lowering is caused by halogen substitution in position 9 (by a factor of 3 for F, >50 for Cl), apparently due to a shortened triplet lifetime caused by heavy atom effect. At 310 nm, both chromophores absorb to a comparable degree and both may react. The reaction at C(20) ketone involves either quite efficient alpha-cleavage (C(17)-C(20)) for compounds bearing an acetal or hydroxyl function at C(17) or less effective (by a factor of ca. 10) hydrogen abstraction from the 18-methyl group in the other cases (finally resulting in Norrish II fragmentation or Yang cyclization). The results allow generalizing how the substitution pattern surrounding each chromophore affects the photoreactivity at that site and the competition between the two modes, allowing predicting the photochemistry of this family of antiinflammatory drugs.

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“…The research in our group in the mid- to late 1960s focused on various aspects of ketone photochemistry, including studies which probed the effect of structure on photochemical behavior of cyclohexadienones ring-fused cyclohexenones, and other systems. We used Hammond’s techniques more and more to determine which photochemical reactions involved singlet excited states and which involved triplet excited states. , Using triplet counting techniques based on precisely executed quenching studies, we were finally able to demonstrate convincingly that the rearrangements of α-santonin and other 2,5-cyclohexadienones occur via short-lived triplet excited states with lifetimes in the nanosecond time domain …”

Section: Early Years At Nyu: 1961–1968mentioning

confidence: 99%

Reflections on a Fifty-Year Career in Organic Photochemistry: A Personal Perspective

Schuster

2013

J. Org. Chem.

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This Perspective traces the career of the author in the area of mechanistic organic photochemistry from the primitive state of this field in the late 1950s and early 1960s until its maturity as a highly sophisticated discipline at the present time. The paper focuses on early studies carried out by the author and his associates to delineate mechanisms of basic types of photochemical reactions of small organic molecules to studies in recent years involving photoinduced electron-transfer processes occurring in nanoscale artificial photosynthetic systems in ultrashort time domains. The important role that serendipitous events played in directing key career decisions and events is emphasized. The important ways that developments in instrumentation influenced the choices, possibilities, and accomplishments of performing research in photochemistry between 1960 and the present time are emphasized. Acknowledgment is given by the author to the many people who contributed directly and indirectly to the course that his career has taken over more than half a century.

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Photochemistry of unsaturated ketones in solutions. XXVII. Synthesis and photochemistry of .DELTA.1-4-alkyltestosterones

Cited by 9 publications

References 3 publications

Noncommunicating Photoreaction Paths in Some Pregna-1,4-diene-3,20-diones

Noncommunicating Photoreaction Paths in Some Pregna-1,4-diene-3,20-diones

General Patterns in the Photochemistry of Pregna-1,4-dien-3,20-diones

Reflections on a Fifty-Year Career in Organic Photochemistry: A Personal Perspective

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