The development of one-pot imine formation and asymmetric Pictet-Spengler reactions cocatalyzed by a chiral thiourea benzoic acid is described. Optically active tetrahydro-beta-carbolines, ubiquitous structural motifs in biologically natural products, are obtained high ee directly from tryptamine aldehyde precursors.

This Account provides an overview of our recent efforts to uncover the fundamental charge transport properties Si-Si and Ge-Ge single bonds introduce useful functions into group 14 molecular wires. We utilize tools chemical synthesis a scanning tunneling microscopy-based break-junction technique study mechanism in these systems. evaluated ability silicon, germanium, carbon wires by comparing conductances within families well-defined structures, members which differ only number Si (or Ge or...

An investigation of the mechanism benzoic acid/thiourea co-catalysis in asymmetric Pictet-Spengler reaction is reported. Kinetic, computational, and structure-activity relationship studies provide evidence that rearomatization via deprotonation pentahydro-β-carbolinium ion intermediate by a chiral thiourea·carboxylate complex both rate- enantioselectivity-determining. The thiourea catalyst induces rate acceleration over background mediated acid alone stabilizing every transition state...

Convenient strategies for the deconstruction and reprocessing of thermosets could improve circularity these materials, but most approaches developed to date do not involve established, high-performance engineering materials. Here, we show that bifunctional silyl ether, i.e., R'O-SiR2-OR'', (BSE)-based comonomers generate covalent adaptable network analogues industrial thermoset polydicyclopentadiene (pDCPD) through a novel BSE exchange process facilitated by low-cost food-safe catalyst...

Abstract Silanes are important compounds in industrial and synthetic chemistry. Here, we develop a general approach for the synthesis of disilanes as well linear cyclic oligosilanes via reductive activation readily available chlorosilanes. The efficient selective generation silyl anion intermediates, which arduous to achieve by other means, allows various novel heterocoupling. In particular, this work presents modular variety functionalized cyclosilanes, may give rise materials with distinct...

A one-pot condensation of isotryptamines and aldehydes that affords enantiomerically enriched 4-substituted tetrahydro-γ-carbolines is reported. The reaction induced by a chiral thiourea/benzoic acid dual catalyst system. Purification the N-Boc-protected products trituration or crystallization provides optically pure tetrahydro-γ-carboline derivatives in scalable highly practical procedure.

Bulk silicon, the bedrock of information technology, consists deceptively simple electronic structure just Si-Si σ bonds. Diamond has same lattice as yet two materials have dramatically different properties. Here we report specific synthesis and electrical characterization a class molecules, oligosilanes, that contain strongly interacting bonds, essential components bulk semiconductor. We used scanning tunneling microscope-based break-junction technique to compare single-molecule conductance...

Modern technologies depend on the semiconductor silicon. Silicon nanostructures evince compelling properties including luminescence and biodegradability. Silicon-based soft matter is less explored, despite attractive of conjugated polymers small molecules inspired by crystalline This perspective describes major synthetic approaches to polysilanes summarizes innovations in preparation structurally complex functional that combine unusual conjugation phenomena, solution processability,...

While the electrical conductivity of bulk-scale group 14 materials such as diamond carbon, silicon, and germanium is well understood, there a gap in knowledge regarding these at nano molecular scales. Filling this important because integrated circuits have shrunk so far that their active regions, which rely heavily on silicon germanium, begin to resemble ornate molecules rather than extended solids. Here we unveil new approach for synthesizing atomically discrete wires present first...

BN 2-vinylnaphthalene, a aromatic vinyl monomer, is copolymerized with styrene under free radical conditions. Oxidation yields styrene-vinyl alcohol (SVA) statistical copolymers tunable hydroxy group content. Comprehensive spectroscopic investigation provides proof of structure. Physical properties that vary systematically content include solubility and glass transition temperature. polymers represent platform for the preparation diverse functional polymeric architectures via remarkable...

We characterize electron transport across Au–molecule–Au junctions of heterogeneous carboxyl and methyl sulfide terminated saturated conjugated molecules. Low-bias conductance measurements are performed using the scanning tunneling microscopy based break-junction technique in presence solvents at room temperature. For a series alkanes with 1–4 carbon atoms hydrocarbon chain, our results show an exponential decrease increasing molecule length characterized by decay constant 0.9 ± 0.1 per...

Here we demonstrate for the first time that strained silanes couple directly to gold electrodes in break-junction conductance measurements. We find silicon molecular wires terminated by alkyl sulfide aurophiles behave effectively as single-molecule parallel circuits with competing sulfur-to-sulfur (low G) and sulfur-to-silacycle (high pathways. can switch off high conducting pathway altering environment of electrode surface disable Au-silacycle coupling. Additionally, between conductive...

Molecular electronics demands complex functional molecules with multiple pathways connecting electrode leads. We report the synthesis and study of a set based on fluorene-like design in which atomic connectors are used to introduce two for conductance. This manuscript details structural underlying rationale developing high conductance these molecular circuit components.

Abstract We report a strategic synthesis of poly(cyclosilane), well‐defined polymer inspired by crystalline silicon. The synthetic strategy relies on the design functionalized cyclohexasilane monomer for transition‐metal‐promoted dehydrocoupling polymerization. Our approach takes advantage dual function phenylsilyl group, which serves crucial role both in novel α,ω‐oligosilanyl dianion and as latent electrophile. show that prefers chair conformation. ensures enhanced reactivity...

We report herein the influence of skeletal connectivity on conformation-dependent optical properties cyclosilane homo- and copolymers. 1,3-Linked cyclosilanes were bathochromically shifted by 20 nm in solution relative to 1,4-linked cyclosilanes, an effect reproduced quantum chemical calculations oligomeric model systems. Polysilane are conformation-dependent, 1,3-linked hypothesized adopt a favorable conformation unavailable constrained endocyclic gauche conformation. Copolymerization...

The tearing of a polymer network arises from mechanochemically coupled bond-breaking events in the backbone chain. An emerging research area is identification molecular strategies for toughening, such as strategic placement reactive groups (e.g., scissile mechanophores) crosslinks instead load-bearing primary strands. These mechanically labile crosslinkers have typically relied on release ring strain or weak covalent bonds selective bond scission. Here, we report novel chemical design...

The direct synthesis of Si–Si dimeric 9-dimethylsilafluorene, structural characterization via single crystal X-ray diffraction studies, and electrochemical redox chemistry with DFT electronic analysis is reported herein.

The gram-scale polymerization of a novel azaborine vinyl monomer is reported.

Silicon nanomaterials combine earth abundance and biodegradability with exceptional electronic properties. Strategic synthesis promises access to novel architectures well-defined surface structure, size, shape. Herein, we describe a five-step of functional macrocyclic polysilanes. Comparison the materials isolated from isomeric building blocks provides evidence that block directionality controls shape resulting nanomaterial. Infrared (IR) 1H 29Si NMR spectroscopies, coupled computational...

BN 2-vinylnaphthalene (BN2VN) is a novel precursor to vinyl alcohol copolymers via sodium hydroperoxide oxidation. We show that the unusual aromaticity of heterocycle leads styrene-like reactivity. Computational data including structural parameters and nucleus independent chemical shift (NICS) values support naphthalene side chain BN2VN. Styrene (St) BN2VN reactivity ratios (r1(BN2VN) = 0.423; r2(St) 2.30; r1r2 0.97) were determined by nonlinear least-squares (NLLS) statistical methods....

Extended azaborine heterocycles are promising biomedical and electronic materials.

While the single-molecule conductance properties of π-conjugated and σ-conjugated systems have been well-studied, little is known regarding mixed σ–π backbone wires factors that control their transport properties. Here we utilize a scanning tunneling microscope-based break-junction technique to study series molecular with π–σ–π structures, where π-moiety an electrode-binding thioanisole ring σ-moiety triatomic α–β–α chain composed C, Si, or Ge atoms. We find sequence composition group 14...

The cis- and trans-isomers of a silacycloheptene were selectively synthesized by the alkylation silyl dianion, novel approach to strained cycloalkenes. trans-silacycloheptene (trans-SiCH) was significantly more than cis isomer, as predicted quantum chemical calculations confirmed crystallographic signatures twisted alkene. Each isomer exhibited distinct reactivity toward ring-opening metathesis polymerization (ROMP), where only trans-SiCH afforded high-molar-mass polymer under...

A class of hybrid oligosilane–arene materials outperforms the σ- and π-conjugated parent structures.