Reexamination of the thermolytic rearrangement of 4-halophenyl azides to 2-aminophenols and other products

Summary The halogenation of derivatives of 2-aminophenol with N-chloro- and N-bromosuccinimides at ambient temperatures in acetic acid was studied. With the necessary compounds available, a reexamination of the thermolytic rearrangement of 2-halophenyl azides to 2-aminophenols and other products was undertaken. It is certain that the rearrangement of 4-halophenyl azides to 2-aminophenols occurs but the products identified in this study differ significantly from those reported previously by Suschitzky et al. (1963, 1966).

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Neuuntersuchung der thermolytischen Umlagerung von 4-Halogenphenylaziden zu 2-Aminophenolen und anderen Produkten

Zusammenfassung Es wurde die Halogenierung von 2-Aminophenol-Derivaten mit N-Chlor- und N-Bromsuccinimid bei Raumtemperatur in Essigsäure untersucht. Mit den zur Verfügung stehenden Verbindungen konnte eine Neuuntersuchung der thermolytischen Umlagerung von 4-Halogenphenylaziden zu 2-Aminophenolen und anderen Produkten unternommen werden. Diese Umlagerung findet sicherlich statt, allerdings differieren die dabei beobachteten Produkte signifikant von denen, die Suschitzky et al. 1963 und 1966 beschrieben.

     

Magnetic resonance studies of the deuteration effect on intersystem crossing in the anthracene molecule

The intersystem crossing decay constants from the ³B_2u state into the ground state of anthracene-d₁₀ in a phenazine crystal have been determined by magnetic resonance techniques at 1.5°K both at high magnetic field and, by a parameterization procedure, at zero magnetic field. A comparison of the anthracene-d₁₀ zero-field results with those for anthracene-h₁₀ show the effects of deuterium substitution to be largest for the in-plane spin levels of the anthracene triplet state.     

Optically detected zero-field triplet state magnetic resonance in photosynthetic bacteria

Triplet state transitions of the photosynthetic bacteria Rhodospirillum Rubrum, Rhodopseudomonas Spheroides and Chromatium Vinosum in chemically reduced preparations have been observed by zero-field optical detection of magnetic resonance at 2 K. For each bacterial preparation two sharp, structureless, zero-field EPR transitions were observed as microwave-induced decreases in the fluorescence intensity of the frozen cellular preparations. The depopulating rate constants for the spin sublevels of the triplet states observed in R Rubrum and R Spheroides were also measured. The similarities of the triplet state frequencies, spectral features and intersystem crossing rates suggest a common structure for the reaction centers in the photosynthetic bacteria.     

The practical synthesis of a novel and highly potent analogue of bryostatin

Macrocycle 1 is a new highly potent analogue of bryostatin 1, a promising anti-cancer agent currently in human clinical trials. In vitro, 1 displays picomolar affinity for PKC and exhibits over 100-fold greater potency than bryostatin 1 when tested against various human cancer cell lines. Macrocycle 1 can be generated in clinically required amounts by chemical synthesis in only 19 steps (LLS) and represents a new clinical lead for the treatment of cancer.     

Triplet state properties of the benzo[α]pyrene-DNA complex as determined by optically detected zero-field magnetic resonance

The zero-field transitions in the photoexcited triplet state of benzo[α]pyrene bound to DNA have been observed by optical detection of magnetic resonance of 2 K. The transition frequencies individual spin sublevel intersystem crossing rates were measured by monitoring the microwave-induced intensity changes of the triplettriplet absorption at 465.8 nm. The triplet state zero-field splitting and dynamics for the benzo[α]pyrene DNA complex are compared with these properties measured for benzo(α)pyrene in other solvent systems.