Cyclische Dipnictadialane

Bei Umsetzungen der AlI-Verbindung Cp3tAl mit Triphosphiranen (PAr)3 (Ar=Mes, Dip, Tip) ist es gelungen, Lewis-basenfreie cyclische Diphosphadialane herzustellen, bei denen sowohl das Al- als auch das P-Atom drei Substituenten tragen. Mit den sterisch anspruchsvolleren Dip- und Tip-Substituenten wurden die ersten 1,2-Diphospha-3,4-dialuminacyclobutane erhalten, während mit Mes-Substituenten [Cp3tAl(μ-PMes)]2 gebildet wird. Diese abweichende Reaktivität wurde durch DFT-Studien bestätigt, die auf eine thermodynamische Präferenz für die 1,2-Diphospha-3,4-dialuminacyclobutane für sterisch anspruchsvollere Gruppen am Phosphor hinwiesen. Mithilfe von Cp*Al konnten wir dieses Konzept auf die entsprechenden cyclischen Diarsadialane [Cp*Al(μ-AsAr)]2 (Ar=Dip, Tip) ausdehnen und zusätzlich die Phosphorvarianten [Cp*Al(μ-PAr)]2 (P=Mes, Dip, Tip) synthetisieren. Die Reaktivität von [Cp3tAl(μ-PPh)]2 gegenüber NHCs wurde untersucht und führte zu doppelt NHC-stabilisiertem [Cp3t(IiPr2)Al(μ-PPh)]2

D-cycloserine augmentation of exposure-based cognitive behavior therapy for anxiety, obsessive-compulsive, and posttraumatic stress disorders: a systematic review and meta-analysis of individual participant data

Importance: Whether and under which conditions D-cycloserine (DCS) augments the effects of exposure-based cognitive behavior therapy for anxiety, obsessive-compulsive, and posttraumatic stress disorders is unclear. Objective: To clarify whether DCS is superior to placebo in augmenting the effects of cognitive behavior therapy for anxiety, obsessive-compulsive, and posttraumatic stress disorders and to evaluate whether antidepressants interact with DCS and the effect of potential moderating variables. Data Sources: PubMed, EMBASE, and PsycINFO were searched from inception to February 10, 2016. Reference lists of previous reviews and meta-analyses and reports of randomized clinical trials were also checked. Study Selection: Studies were eligible for inclusion if they were (1) double-blind randomized clinical trials of DCS as an augmentation strategy for exposure-based cognitive behavior therapy and (2) conducted in humans diagnosed as having specific phobia, social anxiety disorder, panic disorder with or without agoraphobia, obsessive-compulsive disorder, or posttraumatic stress disorder. Data Extraction and Synthesis: Raw data were obtained from the authors and quality controlled. Data were ranked to ensure a consistent metric across studies (score range, 0-100). We used a 3-level multilevel model nesting repeated measures of outcomes within participants, who were nested within studies. Results: Individual participant data were obtained for 21 of 22 eligible trials, representing 1047 of 1073 eligible participants. When controlling for antidepressant use, participants receiving DCS showed greater improvement from pretreatment to posttreatment (mean difference, -3.62; 95% CI, -0.81 to -6.43; P = .01; d = -0.25) but not from pretreatment to midtreatment (mean difference, -1.66; 95% CI, -4.92 to 1.60; P = .32; d = -0.14) or from pretreatment to follow-up (mean difference, -2.98, 95% CI, -5.99 to 0.03; P = .05; d = -0.19). Additional analyses showed that participants assigned to DCS were associated with lower symptom severity than those assigned to placebo at posttreatment and at follow-up. Antidepressants did not moderate the effects of DCS. None of the prespecified patient-level or study-level moderators was associated with outcomes. Conclusions and Relevance: D-cycloserine is associated with a small augmentation effect on exposure-based therapy. This effect is not moderated by the concurrent use of antidepressants. Further research is needed to identify patient and/or therapy characteristics associated with DCS response.2018-05-0

Phosphine-catalysed reductive coupling of Dihalophosphanes

Classically, tetraorgano diphosphanes have been synthesized through Wurtz-type reductive coupling of halophosphanes R2PX or more recently, through the dehydrocoupling of phosphines R2PH. Catalytic variants of the dehydrocoupling reaction have been reported but are limited to R2PH compounds. Using PEt3 as a catalyst, we now show that TipPBr2 (Tip = 2,4,6-iPr3C6H2) is selectively coupled to give the dibromodiphosphane (TipPBr)2 (1), a compound not accessible using classic Mg reduction. Surprisingly, when using DipPBr2 (Dip = 2,6-iPr3C6H3) in the PEt3-catalysed reductive coupling the diphosphene (PDip)2 (2) with a P=P double was formed selectively. In benzene solutions (PDip)2 has a half life-time of ca. 28 days and can be utilized with NHCs to access NHC-phosphinidene adducts. Control experiments show that [BrPEt3]Br is a potential oxidation product in the catalytic cycle, which can be then debrominated by using Zn dust as sacrificial reductant

Metal-free NH-oxidative addition at phospha-Wittig reagents

N-containing molecules are mostly derived from ammonia (NH3). Ammonia activation has been demonstrated for single transition metal centers as well as for low-valent main group species. Phosphinidenes, mono-valent phosphorus species, can be stabilized by phosphines, giving so-called phosphanylidenephosphoranes of the type RP(PR’3). We demonstrate the facile, metal-free NH3 activation using ArP(PMe3), affording for the first time isolable secondary aminophosphines ArP(H)NH2 through oxidative addition at a phosphinidenoid P atom. DFT studies reveal that two molecules of NH3 act in concert to facilitate an NH3 for PMe3 exchange. Furthermore, H2NR and HNR2 activation is demonstrated

Terphenyl(bisamino)phosphines: Electron-rich Ligands for Gold-Catalysis

Terphenyl(bisamino)phosphines have been identified as effective ligands in cationic gold(I) complexes for the hydroamination of acetylenes. These systems are related to Buchwald phosphines and their steric properties have been evaluated. Effective hydroamination was noted even at low catalyst loadings and a series of cationic gold(I) complexes has been structurally characterized clearly indicating stabilizing effects through gold-arene interactions