Theano is a linear algebra compiler that optimizes a user's symbolically-specified mathematical computations to produce efficient low-level implementations. In this paper, we present new features and efficiency improvements to Theano, and benchmarks demonstrating Theano's performance relative to Torch7, a recently introduced machine learning library, and to RNNLM, a C++ library targeted at recurrent neural networks.

Ambiphilic phosphine−borane derivatives 1-B(OR) 2 -2-PR′ 2 −C 6 H 4 (R′ = Ph (1), iPr (2); (OR) 2 = (OMe) 2 (1a, 2a); catechol (1b, 2b) pinacol (1c, 2c), −OCH 2 C-(CH 3 ) 2 CH 2 O− (1d)) were tested as catalysts for the hydroboration of CO 2 using HBcat or BH 3 ·SMe 2 to generate methoxyboranes. It was shown that the most active species were the catechol derivatives 1b and 2b. In the presence of HBcat, without CO 2 , ambiphilic species 1a, 1c, and 1d were shown to transform to 1b, whereas 2a and 2c were shown to transform to 2b. The formaldehyde adducts 1b·CH 2 O and 2b· CH 2 O are postulated to be the active catalysts in the reduction of CO 2 rather than being simple resting states. Isotope labeling experiments and density functional theory (DFT) studies show that once the formaldehyde adduct is generated, the CH 2 O moiety remains on the ambiphilic system through catalysis. Species 2b·CH 2 O was shown to exhibit turnover frequencies for the CO 2 reduction using BH 3 ·SMe 2 up to 228 h −1 at ambient temperature and up to 873 h −1 at 70°C, mirroring the catalytic activity of 1b.

The ansa-aminohydroborane 1-NMe2 -2-(BH2 )C6 H4 crystallizes in an unprecedented type of dimer containing a B-H bond activated by one FLP moiety. Upon mild heating and without the use of any catalyst, this molecule liberates one equivalent of hydrogen to generate a diborane molecule. The synthesis and structural characterization of these new compounds, as well as the kinetic monitoring of the reaction and the DFT investigation of its mechanism, are reported.

While the organotrifluoroborate group is commonly used as a leaving group in cross-coupling reactions, we now show that their high stability can be used to protect the Lewis acidic moieties of frustrated Lewis pair catalysts. Indeed, the air and moisture-stable trifluoro- and difluoroborate derivatives of bulky (tetramethylpiperidino)benzene are shown to be conveniently converted to their dihydroborane analogue which is known to activate small molecules. An efficient synthesis route to these stable and convenient precatalysts, their deprotection chemistry and their benchtop use for the dehydrogenative borylation of heteroarenes is presented.