An investigation of the chemistry of the tert-butyl-substituted molybdenocene system, {(Cp Bu t) 2 Mo} (Cp Bu t = C 5 H 4 Bu t ), has demonstrated that the η 2 -acetonitrile ligand in (Cp Bu t ) 2 Mo(η 2 -MeCN) may be alkylated by RI (R = Me, Et) at nitrogen to give iminoacyl derivatives, [(Cp Bu t ) 2 Mo(η 2 -MeC᎐ ᎐ NR)] ϩ , which is a new type of reactivity for mononuclear acetonitrile complexes. A series of chalcogenolate-hydride complexes (Cp Bu t ) 2 Mo(EPh)H (E = S, Se, Te) have been obtained by reaction of (Cp Bu t ) 2 MoH 2 with Ph 2 E 2 , and may be alkylated by MeI to give the chalcogenoether adducts [(Cp Bu t ) 2 Mo(PhEMe)H]I. Dynamic NMR studies on [(Cp Bu t ) 2 Mo(PhEMe)H]ϩ indicate that the barrier to inversion at the chalcogen increases in the sequence S < Se < Te. The oxo complex (Cp Bu t ) 2 MoO reacts with 2 equivalents of Me 3 SiX (X = Cl, Br, I, O 2 CMe, O 3 SMe) to yield (Cp Bu t) 2 MoX 2 ; for X = CN and NCS, (Cp Bu t ) 2 -Mo(OSiMe 3 )X, the product of reaction with 1 equivalent may be isolated. (Cp Bu t) 2 Mo(OSiMe 3 )X (X = CN, NCS) reacts with Me 3 SiNCS to give the thiocyanate complex (Cp Bu t ) 2 Mo(SCN)X, rather than the isocyanate isomer, (Cp Bu t) 2 Mo(NCS)X, thereby indicating that the reactions do not involve a simple metathesis of the Si-NCS bond. Other complexes that are reported include:
The reaction of 2-halobenzyl halides with the borate anion Li[(Ph)(t-Bu)Bpin] leads not only to the expected arylation at the benzyl position, but also to some Suzuki biaryl cross-coupling. Preliminary mechanistic investigations hint towards the intermediacy of benzyl iron intermediates that can either: (a) directly cross-couple with the aryl boron reagent to give observed monoarylated species, or (b) undergo oxidative addition of the aryl halide to generate the diarylated species on reaction with the boron-based nucleophile.
The prognosis for glioblastoma has remained poor despite multimodal standard of care (SOC) treatment, including temozolomide, radiation, and surgical resection. Further, the addition of immunotherapies, while promising in a number of other solid tumors, has overwhelmingly failed in the treatment of gliomas, in part due to the immunosuppressive microenvironment and poor drug penetrance to the brain. Local delivery of immunomodulatory therapies circumvents some of these challenges and has led to long-term remission in select patients. Many of these approaches utilize convection-enhanced delivery (CED) for immunological drug delivery, allowing high doses to be delivered directly to the brain parenchyma, avoiding systemic toxicity. Here, we review the literature encompassing immunotherapies delivered via CED – from preclinical model systems to clinical trials – and explore how their unique combination elicits an anti-tumor response by the immune system, decreases toxicity and improves survival among select high-grade glioma patients.
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