Recent developments in isocyanide based multicomponent reactions in applied chemistry

http://aether.cmi.ua.ac.be/artikels/Artikels%20Gitte/Artikels/Reviews/Trans.%20Metal.%20catal.%20reactions%20Chem.%20rev.%20042127.pdf

Transition-Metal-Catalyzed Reactions in Heterocyclic Synthesis

The review covers the knowledge on photoremovable protecting
groups and includes all relevant chromophores studied in the
time period of 2000–2012; the most relevant earlier works are
also discussed.

/pdf/photoremovable-protecting-groups-in-chemistry-and-biology-2n33qs6p7b.pdf

Photoremovable Protecting Groups in Chemistry and Biology: Reaction Mechanisms and Efficacy

Isatins As Privileged Molecules in Design and Synthesis of Spiro-Fused Cyclic Frameworks

The development of colloidal quantum dots has led to practical applications of quantum confinement, such as in solution-processed solar cells1, lasers2 and as biological labels3. Further scientific and technological advances should be achievable if these colloidal quantum systems could be electronically coupled in a general way. For example, this was the case when it became possible to couple solid-state embedded quantum dots into quantum dot molecules4,5. Similarly, the preparation of nanowires with linear alternating compositions—another form of coupled quantum dots—has led to the rapid development of single-nanowire light-emitting diodes6 and single-electron transistors7. Current strategies to connect colloidal quantum dots use organic coupling agents8,9, which suffer from limited control over coupling parameters and over the geometry and complexity of assemblies. Here we demonstrate a general approach for fabricating inorganically coupled colloidal quantum dots and rods, connected epitaxially at branched and linear junctions within single nanocrystals. We achieve control over branching and composition throughout the growth of nanocrystal heterostructures to independently tune the properties of each component and the nature of their interactions. Distinct dots and rods are coupled through potential barriers of tuneable height and width, and arranged in three-dimensional space at well-defined angles and distances. Such control allows investigation of potential applications ranging from quantum information processing to artificial photosynthesis.

Colloidal nanocrystal heterostructures with linear and branched topology

This Account focuses mainly on our recent endeavors in the area of multicomponent reactions (MCRs) involving zwitterionic species generated by the addition of isocyanides and nucleophilic carbenes such as dimethoxycarbene and N-heterocyclic carbenes to activated alkynes. The strategy employed encompasses the interception of 1:1 zwitterionic species, generated in situ with a wide range of electrophiles. The new MCRs developed offer an efficient and convenient entry into several heterocycles of biological and synthetic importance.

Strategies for heterocyclic construction via novel multicomponent reactions based on isocyanides and nucleophilic carbenes.

A novel synthesis of 2-aminopyrroles using a three-component reaction.

Fast release of biological stimulants is needed to monitor physiological response in real time.1 p-Hydroxyphenacyl (pHP) phototriggers meet this requirement. Moreover, the side products are biologically compatible and transparent to excitation wavelengths >300 nm.2 Knowledge of the release rate is essential to biophysical applications. Givens et al. identified a short-lived triplet state as the reactive excited state of pHP phosphates and carboxylates on the basis of quenching experiments.2 In a recent study of pHP esters Zhang et al.3a questioned that evidence and favored a singlet mechanism. Here, we prove that the reactive excited state of pHP diethyl phosphate (1) is a very short-lived triplet state and we provide direct evidence for adiabatic tautomerization of p-hydroxyacetophenone and its derivatives in the triplet state.

p-Hydroxyphenacyl Phototriggers: The Reactive Excited State of Phosphate Photorelease

The photodissociation of benzoin diethyl phosphate (1, “caged” phosphate) was studied by nanosecond and picosecond laser flash photolysis. The lowest triplet state of 1, 31, was identified as the reactive excited state with an absorption maximum around 340 nm and a lifetime of 10−25 ns, depending on the solvent. Two different reaction paths were identified, both of which involve the release of diethyl phosphoric acid from 31 within 25 ns. In addition to a fast cyclization−elimination process leading to 2-phenylbenzofuran (2) and diethyl phosphoric acid, heterolytic adiabatic dissociation of 31 yields a triplet cation and diethyl phosphate anion in water, trifluoroethanol, and hexafluoro-2-propanol solutions. The triplet cation (570 nm, τ ≈ 430 ns in water) undergoes intersystem crossing to the singlet ground state before it reacts with the solvent molecules.

Kinetics and Mechanism of Phosphate Photorelease from Benzoin Diethyl Phosphate: Evidence for Adiabatic Fission to an α-Keto Cation in the Triplet State

The synthesis and photophysical characterization of a series of free base and zinc porphyrin containing, Newkome-type dendrimers terminated with anthraquinone groups (FbP-Ga-AQn and ZnP-Ga-AQn) and ethyl groups (FbP-Ga-Etn and ZnP-Ga-Etn) are described. These dendrimers were designed for use as mimics of the photosynthetic reaction center. Red-shifts in the absorption spectra, particularly in the anthraquinone-terminated series, were interpreted as resulting from backfolding of the dendrimer branches. Dendrimers FbP-Ga-AQn were shown to exhibit substantial quenching (58−75%) of the porphyrin fluorescence as measured against the analogous ethyl-terminated dendrimers (FbP-Ga-Etn) in steady-state fluorescence experiments. The zinc porphyrin containing dendrimers ZnP-Ga-AQn exhibited nearly complete quenching (96−99.5%) of the porphyrin fluorescence. An intramolecular electron-transfer mechanism is proposed for the substantial decrease in fluorescence in both series of dendrimers. Time-resolved fluorescence e...

C. Rajesh

Papers

Strategies for heterocyclic construction via novel multicomponent reactions based on isocyanides and nucleophilic carbenes.

A novel synthesis of 2-aminopyrroles using a three-component reaction.

p-Hydroxyphenacyl Phototriggers: The Reactive Excited State of Phosphate Photorelease

Kinetics and Mechanism of Phosphate Photorelease from Benzoin Diethyl Phosphate: Evidence for Adiabatic Fission to an α-Keto Cation in the Triplet State

Photoinduced Electron-Transfer within Free Base and Zinc Porphyrin Containing Poly(Amide) Dendrimers