Effects of extending the π-conjugation of the acetylide ligand on the photophysics and reverse saturable absorption of Pt(ii) bipyridine bisacetylide complexes.

The synthesis and photophysics of four platinum(ii) bipyridine (bpy) bisacetylide complexes with different degrees of π-conjugation and an electron-donating diphenylamino (NPh2) or electron-withdrawing benzothiazolyl (BTZ) terminal substituent on the acetylide ligands are reported. The UV-vis absorption spectra of these complexes are composed of intense ligand-localized 1π,π* transitions at 330-430 nm and broad, moderately strong ligand-to-ligand charge transfer/metal-to-ligand charge transfer (1LLCT/1MLCT) transitions at 430-530 nm. All complexes are phosphorescent in solutions at room temperature and exhibit very broad and moderately strong triplet excited-state absorption in the visible to the NIR spectral region (425-800 nm). It is found that extending the π-conjugation of the acetylide ligands via adding one or two more ethynylfluorenyl unit(s) to the acetylide ligand does not change the energies of the 1π,π* and 1LLCT/1MLCT transitions pronouncedly except for increasing the molar extinction coefficients of the 1π,π* transitions. The emitting triplet excited states of the four complexes are the 3MLCT/3LLCT states and have the same energy. However, the complex that contains the tris(ethynylfluorenyl) units and the terminal NPh2 substituent on the acetylide ligand exhibits longer triplet lifetimes than the corresponding complex that has the bis(ethynylfluorenyl) units. The transient absorption band maxima of the complexes with tris(ethynylfluorenyl) units are slightly red-shifted in comparison to those of their respective counterparts with bis(ethynylfluorenyl) units. The nature of the terminal substituent does not influence the parentage and energies of the lowest singlet and triplet excited states. However, the triplet excited-state lifetimes of the complexes with the NPh2 terminal substituent on the bis(ethynylfluorenyl) or tris(ethynylfluorenyl) ligands are much longer than that of their counterpart with monofluorenylacetylide ligands; while the triplet lifetimes of the complexes containing the BTZ terminal substituent are similar to their counterpart with monofluorenylacetylide ligands. All complexes exhibit strong reverse saturable absorption (RSA) at 532 nm for nanosecond laser pulses.

Asymmetric cyclization reactions of allenoates with imines or α,ß-unsaturated ketones catalyzed by organocatalysts derived from cinchona alkaloids.

Lewis base-catalyzed cyclization reactions of allenoates with electron-deficient olefins and imines have been demonstrated by the preparation of biologically active natural products and pharmaceutically interesting substances and have emerged as powerful synthetic tools in the rapid construction of cyclic molecular complexity. In contrast to phosphine-containing Lewis bases, nitrogen-containing Lewis base amines display markedly different reaction profiles; however, this area is not well-developed. Herein we summarize the recent progress in this emerging field and outline the challenges ahead.

DABCO-catalyzed regioselective cyclization reactions of ß,γ-unsaturated α-ketophosphonates or ß,γ-unsaturated α-ketoesters with allenic esters.

Highly efficient DABCO-catalyzed [4 + 2] cycloaddition of ß,γ-unsaturated α-ketophosphonates or ß,γ-unsaturated α-ketoesters with allenic esters gives the corresponding highly functionalized tetrahydropyran and dihydropyran derivatives in good to excellent yields and moderate to good regioselectivities under mild conditions.

Synthesis of optically active dihydropyrans from asymmetric [4 + 2] cycloaddition of ß,γ-unsaturated α-ketoesters with allenic esters.

ß-Isocupreidine (ß-ICD) catalyzed asymmetric [4 + 2] cycloaddition of ß,γ-unsaturated α-ketoesters with allenic esters afforded ester-substituted functionalized dihydropyran derivatives in high yields along with high enantioselectivities under mild conditions.

Enantioselective synthesis of highly functionalized phosphonate-substituted pyrans or dihydropyrans through asymmetric [4+2] cycloaddition of ß,γ-unsaturated α-ketophosphonates with allenic esters.

Tell me which you want: catalytic asymmetric [4+2] cycloadditions of ß,γ-unsaturated α-ketophosphonates with allenic esters catalyzed by organocatalysts derived from different cinchona alkaloids have been developed, affording phosphonate-substituted functionalized pyran and dihydropyran derivatives in excellent yields with high enantioselectivities under mild conditions. The choice of product is controlled by the hydrogen bonding characteristics of the chosen catalyst.

Multifunctional chiral phosphines-catalyzed highly diastereoselective and enantioselective substitution of Morita-Baylis-Hillman adducts with oxazolones.

Multifunctional chiral phosphine (phosphine-thiourea type) L2-catalyzed allylic substitutions of MBH adducts 1 with oxazolones 2 produce the corresponding optically active adducts 3 in good to excellent yields and ee's as well as moderate to good de's under mild conditions. The synergistic interaction between hydrogen bond donor site and nucleophilic site has been discussed, indicating that finely tuning the active sites of the multifunctional phosphine organocatalysts is very important.

Lysine Demethylase 5A is Required for MYC Driven Transcription in Multiple Myeloma.

Lysine demethylase 5A (KDM5A) is a negative regulator of histone H3K4 trimethylation, a histone mark associated with activate gene transcription. We identify that KDM5A interacts with the P-TEFb complex and cooperates with MYC to control MYC targeted genes in multiple myeloma (MM) cells. We develop a cell-permeable and selective KDM5 inhibitor, JQKD82, that increases histone H3K4me3 but paradoxically inhibits downstream MYC-driven transcriptional output in vitro and in vivo. Using genetic ablation together with our inhibitor, we establish that KDM5A supports MYC target gene transcription independent of MYC itself, by supporting TFIIH (CDK7)- and P-TEFb (CDK9)-mediated phosphorylation of RNAPII. These data identify KDM5A as a unique vulnerability in MM functioning through regulation of MYC-target gene transcription, and establish JQKD82 as a tool compound to block KDM5A function as a potential therapeutic strategy for MM.

Heteroleptic cationic iridium(III) complexes bearing naphthalimidyl substituents: synthesis, photophysics and reverse saturable absorption.

Three heteroleptic cationic iridium(iii) complexes containing a cyclometalating 2-[3-(7-naphthalimidylfluoren-2'-yl)phenyl]pyridine ligand and different diimine (N^N) ligands (N^N = 2,2'-bipyridine (bpy, ), 1,10-phenanthroline (phen, ), and 5,5'-bis[7-(benzothiazol-2'-yl)fluoren-2'-yl]-2,2'-bipyridine (BTF-bpy, )) were synthesized and characterized. The photophysics of these complexes was systematically investigated via spectroscopic methods and by time-dependent density functional theory (TDDFT). All complexes possess a very weak charge-transfer tail at ca. 450-570 nm; and two intense absorption bands in the region of 290-350 nm and 350-450 nm, respectively. The emission of in CH2Cl2 emanates predominantly from the C^N ligand-localized (3)π,π* state. These emitting excited states also give rise to broadband triplet excited-state absorption in the visible to the near-IR region (i.e. 420-800 nm for and , and 460-800 nm for ). The kinetics of fs transient absorption (TA) reveals that the lowest singlet excited-state lifetimes of these complexes vary from 1.43 ps to 142 ps. The stronger excited-state absorption of compared to their respective ground-state absorption in the visible spectral range leads to strong reverse saturable absorption (RSA) at 532 nm for ns laser pulses. The trend of transmission signal decrease follows > > . Extending the π-conjugation of the N^N ligand increases the strength of RSA. In addition, the naphthalimidyl (NI) substitution at the cyclometalating ligand dramatically increases the triplet excited-state lifetimes and broadens the triplet excited-state absorption to the NIR region compared to the respective Ir(iii) complexes with a benzothiazolyl substituent on the cyclometalating ligand.