Cobalt(II)-catalyzed intramolecular C-H amination with phosphoryl azides: formation of 6- and 7-membered cyclophosphoramidates.

A highly effective Co(II)-based system has been developed for catalytic intramolecular C-H amination with phosphoryl azides without the need of terminal oxidant or other additives, resulting in the high-yielding production of cyclophosphoramidates with nitrogen gas as the byproduct. Additional features of this new catalytic system include the amination of primary C-H bonds and formation of 7-membered-ring structures.

Cobalt-catalyzed asymmetric olefin aziridination with diphenylphosphoryl azide.

The cobalt(II) complexes of D2-symmetric chiral porphyrins, such as 3,5-Di(t)Bu-ChenPhyrin P5, can catalyze asymmetric olefin aziridination with diphenylphosphoryl azide (DPPA) as a nitrene source. Acceptable asymmetric inductions were observed for the [Co(P5)]-based catalytic system, forming the desired N-phosphorus-substituted aziridines in moderate to high yields and good enantioselectivities.

A highly effective cobalt catalyst for olefin aziridination with azides: hydrogen bonding guided catalyst design.

[Co(P1)], which was designed on the basis of potential hydrogen-bonding interactions in the metal-nitrene intermediate, is a highly active aziridination catalyst with azides. [Co(P1)] can effectively aziridinate various aromatic olefins with arylsulfonyl azides under mild conditions, forming sulfonylated aziridines in excellent yields. The Co-based system enjoys several attributes associated with the relatively low cost of cobalt and the wide accessibility of arylsulfonyl azides. Furthermore, it generates stable dinitrogen as the only byproduct.

Cobalt-catalyzed aziridination with diphenylphosphoryl azide (DPPA): direct synthesis of N-phosphorus-substituted aziridines from alkenes.

A new catalytic aziridination system that consists of cobalt(II) tetraphenylporphyrin [Co(TPP)] as the catalyst and diphenylphosphoryl azide (DPPA) as the nitrene source has been developed. The cobalt-based catalytic system allows direct synthesis of N-phosphorus-substituted aziridines from alkenes with dinitrogen as the byproduct. Cobalt ion seems essential to the catalytic aziridination with DPPA as no or only trace amounts of the desired products were observed with other metal complexes of tetraphenylporphyrin.

Natural history of intracranial atherosclerosis: a critical review.

Intracranial atherosclerosis is responsible for a significant number of strokes. Medical therapy for this condition may fail, leaving patients at high risk for cerebral infarction and death. With advances in endovascular techniques on the horizon, understanding the prognosis of conservative treatment is essential for appropriate patient management. Although several small studies have attempted to address this issue, a comprehensive review regarding the natural history of intracranial atherosclerosis in a vessel-specific manner is lacking. Owing to heterogeneity in vascular anatomy and physiology, atherosclerosis in different vessels may represent diseases with fundamentally distinct courses. Therefore, it is important to distinguish vascular territories when studying the natural history of this condition. To this end, we critically review the literature investigating medical management of patients with intracranial atherosclerosis, segregating our findings by vessel. Analysis by this method suggests that middle cerebral artery atherosclerosis carries a lower mortality rate than stenoses involving other intracranial vessels, and that asymptomatic disease follows a more benign course. In addition, plaque progression and transcranial Doppler-detected microemboli seem to predict outcome according to limited data. This comprehensive review may help guide clinical decision-making and therapeutic developments in this patient population.

Pilomyxoid astrocytoma: diagnosis, prognosis, and management.

Pilomyxoid astrocytoma (PMA) is a recently defined pediatric brain tumor; PMAs were previously classified within the pilocytic astrocytoma (PA) category. Nevertheless, PMA has different histological features and has been shown to behave more aggressively than PA. These findings indicate that PMA may be a unique entity that is distinct from PA, or it may be an unusual variant. To increase awareness of PMA within the neurosurgical community, the authors review the diagnostic criteria, prognostic implications, and current management of this recently described pediatric low-grade astrocytoma.

Facile sonochemical synthesis of graphite intercalation compounds.

[reaction: see text] Graphite intercalation compounds (GICs) are useful as powerful reducing agents in organic chemistry and are typically prepared by anaerobic solid-state reactions at high temperatures for 1-8 h. We have been able to prepare KC(8) in situ in toluene using ultrasound in less than 5 min. This allows for a convenient approach to reductive chemical syntheses involving GICs.