Wavelength dependency of the relative proportions of singlet/triplet methylenes from the photolysis of diazomethane

Taylor, G.W.; Simons, J. W.

doi:10.1139/v70-168

Cited by 2 publications

(7 citation statements)

References 7 publications

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“…The results obtained in all cases substantiate the original proposal that the photolysis of cyclic sulfites may in fact give rise to species virtually indistinguishable chemically from those produced from conventional carbene precursors such as trans-2,3-diphenyloxirane (23) and phenyldiazomethane (24). Higher yields are obtained with the oxirane 23 and the diazo precursor 24 (Table I), which indicates that the rate of fragmentation of 23 (and 22) exceeds that of 17 and 18.…”

Section: Resultssupporting

confidence: 79%

“…Irradiation (254 nm) of 17 or 18 in cyclohexane gave, as anticipated, the insertion product benzylcyclohexane mechanism of formation of 20 will be discussed later, it is significant that under the reaction conditions investigated no oxiranes are detected, i.e., cfs-2,3-diphenyloxirane (22) in the case of 17 or trans-2,3-dipheny 1oxirane (23) in the case of 18, when the photoreactions were monitored using pmr and thin layer chromatographic techniques. Furthermore, the absence of detectable amounts of stilbene and its dehydrophotocy- clization product phenanthrene among the reaction products indicates that [5 -* 3 + 2] photocycloelimination does not occur to a significant extent with either 17 or 18.…”

Section: Resultssupporting

confidence: 54%

“…Although it is apparent from the chemical data that both 17 and 18 undergo [5 -* 2 + 2 + 1] cycloeliminations to produce "free" carbene, the characteristic phenylcarbene epr signal could not be observed upon photolysis of these substrates for reasons yet undetermined.21 Similar results were observed for 2,3-diphenyloxirane (23) and triphenyloxirane where no epr signal was detected for phenylcarbene (6) despite convincing chemical evidence to the contrary for its formation.20•21 In the absence of direct epr and/or optical spectroscopic data, it was necessary to obtain further chemical proof for the contention that 17 and 18 are indeed phenylcarbene precursors.…”

Section: Resultsmentioning

confidence: 75%

“…Competitive insertion experiments prove particularly useful as a method for comparing divalent carbon species generated from different sources such as 17 and 18.20•22 Gutsche and coworkers22 have previously determined the insertion selectivity of phenylcarbene (6) generated from phenyldiazomethane (24). Additional data on the selectivity of 6 formed from the oxiranes 22 and 23 and the diazo compound 24 were reported by Griffin and coworkers.20 A similar study was initiated of the insertion selectivity of 6 generated from the sulfites 17 and 18 and the conventional precursors 23 and 24 into primary and secondary C-H bonds of pentane.…”

Section: Resultsmentioning

confidence: 99%

“…Further speculation on the origin of these effects is unwarranted at this time in the absence of additional data, although it is noteworthy in this connection that the proportion of ground triplet state methylene produced in the primary photolysis of diazomethane is independent of wavelength at least over the range from 366 to 436 nm. 23 Extensive effort has been devoted to characterizing the multiplicity of the reactive state (s) of phenylcarbene (6). A triplet ground state has been assigned to 6 on the basis of epr13 and optical8* matrix isolation techniques.…”

Section: Resultsmentioning

confidence: 99%

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New precursors for arylcarbenes. Photocycloelimination reactions of cyclic sulfites

Griffin¹,

Manmade²

1972

J. Org. Chem.

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distilled and the residue was chromatographed as described for the preparation above, yielding 0.110 g (0.45 mmol) of 4, 0.417 g (2.24 mmol) of 3, and 1.796 g (9.54 mmol) of 2.C. Uv Irradiation.•-A homogeneous solution of 1.35 g (7.33 mmol) of S4N4, 200 ml of benzene, and 4.15 g (31.39 mmol) of tetrahydronaphthalene was irradiated for 206 hr at room temperature. After removal of the solvent under vacuum at room temperature, the residue was chromatographed. In addition to the unreacted tetrahydronaphthalene, 0.256 g (1.36 mmol) of 2 and 0.067 g (0.36 mmol) of 3 were obtained. Compound 4 was recovered in traces and identified by tic analysis.Reaction of S4N4 with 2.-A 0.748-g (3.97 mmol) sample of 2 in 20 ml of xylene was treated with 1.10 g (5.97 mmol) of S4N4 and the mixture was refluxed for about 8 hr under nitrogen atmosphere with stirring. After removal of the solvent by distillation at 20 Torr, the residue was chromatographed, yielding 0.059 g (0.24 mmol) of 4, 0.229 g (1.23 mmol) of 3, and 0.469 g (2.49 mmol) of 2.Reaction of 2 with Sulfur.-A mixture of 0.109 g (0.58 mmol) of 2 and 0.022 g (0.69 mmol) of sulfur was heated at 250-270°f or 2.5 hr. After cooling the residue gave after crystallization from methanol 0.078 g (0.42 mmol) of 3.

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Section: Resultssupporting

confidence: 79%

Section: Resultssupporting

confidence: 54%

Section: Resultsmentioning

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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New precursors for arylcarbenes. Photocycloelimination reactions of cyclic sulfites

Griffin¹,

Manmade²

1972

J. Org. Chem.

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Macrocyclic Inhibitors of Penicillopepsin. 2. X-ray Crystallographic Analyses of Penicillopepsin Complexed with a P3−P1 Macrocyclic Peptidyl Inhibitor and with Its Two Acyclic Analogues

et al. 1998

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Macrocyclic inhibitor 1 {methyl [cyclo-7[(2R)-((N-valyl) amino)-2-(hydroxyl-(1S)-1-methyoxycarbonyl-2-phenylethoxy)phosphinyloxyethyl]-1-naphthaleneacetamide] sodium salt} was designed according to the conformation of the acyclic analogue Iva-l-Val-l-Val-l-LeuP-(O)Phe-OMe [LeuP = the phosphinic acid and analogue of l-leucine; (O)Phe = l-3-phenyllactic acid; OMe = methyl ester] (4) bound to penicillopepsin, by linking the P1 and P3 side chains of the penicillopepsin inhibitor. This compound and its two acyclic derivatives, {methyl (2S)-[1-(((N-Formyl)-l-valyl)amino-2-(2-naphthyl)ethyl)hydroxyphosphinyloxy]-3-phenylpropanoate, sodium salt} (2) and {methyl (2S)-[1-(((N-(1-naphthaleneacetyl))-l-valyl)aminomethyl)hydroxyphosphinyloxy]-3-phenylpropanoate, sodium salt} (3), have been synthesized and evaluated as inhibitors of penicillopepsin. Their binding affinity to the enzyme was found to be inversely related to the predicted degree of conformational flexibility across the series: 3 (K i = 110 μM), 2 (K i = 7.6 μM), 1 (K i = 0.8 μM). The X-ray crystallographic structures of penicillopepsin complexed with the macrocyclic peptidyl phosphonate 1 and with its two derivatives 2 and 3 have been determined and refined to crystallographic agreement factors R (=Σ||F o| − |F c||/Σ|F o|) of 15.9%, 16.0%, and 15.2% and R free of 19.8%, 20.3%, and 21.4%, respectively. The intensity data for all complexes were collected to 1.5 Å resolution. One 1.25 Å resolution data set was obtained for the complex with 1 at 110 K; the structure was refined to an R factor of 15.0% (R free of 19.7%). The binding interactions that 1 and 2 make with penicillopepsin are similar to those that have been observed for other transition-state mimics with aspartyl proteinases. On the other hand, the acyclic linear inhibitor 3 exhibits distinctive binding to penicillopepsin with the phosphonate group shifted ∼3.0 Å from the average position observed for the other complexes. These structural results show that the macrocyclic constraint of 1 enhances its binding affinity over those of the acyclic analogues but the differences in the observed bound dispositions mean that the effect has yet to be quantified.

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Wavelength dependency of the relative proportions of singlet/triplet methylenes from the photolysis of diazomethane

Cited by 2 publications

References 7 publications

New precursors for arylcarbenes. Photocycloelimination reactions of cyclic sulfites

New precursors for arylcarbenes. Photocycloelimination reactions of cyclic sulfites

Macrocyclic Inhibitors of Penicillopepsin. 2. X-ray Crystallographic Analyses of Penicillopepsin Complexed with a P3−P1 Macrocyclic Peptidyl Inhibitor and with Its Two Acyclic Analogues

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