Transition metal-free synthesis of sterically hindered allylarenes from 5-hexene-2-one

A simple, efficient and transition metal-free strategy was established for the synthesis of highly functionalized, sterically hindered allylarenes (6, 7 & 8) by base-mediated ring transformation of 2-oxo-6-aryl-4-(methylthio/sec-amino)-2H-pyran-3-carbonitriles (3/4) with 5-hexene-2-one (5). This provides a method for the synthesis of allylarenes functionalized with different electron donating and withdrawing groups in one pot. The structures of isolated products 6c and 7a were ascertained by spectroscopic and single crystal X-ray diffraction analyses. In addition, we have performed a molecular docking study to predict the biological activity of the synthesized molecules for binding to estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ).

The Pd(0) and Pd(ii) cocatalyzed isomerization of alkynyl epoxides to furans: a mechanistic investigation using DFT calculations

The conversion of alkynyl epoxides to furans is an unusual tandem catalytic process in which two different oxidation states of palladium are employed. In this study, we used density functional theory calculations to establish the mechanistic details of the catalytic cycles for all the individual processes in this conversion. The results showed that the use of Pd(0) or Pd(ii) alone as the catalyst leads to high reaction barriers. This finding is consistent with experimental observations of low furan yields and the need for high temperatures in the presence of either catalyst alone. However, a combination of Pd(0) and Pd(ii) lowers the reaction barriers considerably. Our key finding is that the reaction pathway involves epoxide ring opening catalyzed by Pd(0), followed by tautomerization of an enol to generate an allenyl ketone in conjunction with Pd(0), with a subsequent Pd(ii)-catalyzed cyclization to yield the furan.

Synthesis of fluorenyl alcohols via cooperative palladium/norbornene catalysis

Herein, we report a novel catalytic synthesis of substituted 9H-fluoren-9-ols starting from aryl iodides and secondary ortho-bromobenzyl alcohols in the presence of palladium/norbornene as a catalytic system. The present protocol exhibits high functional group tolerance, mild reaction conditions and moderate to good yields. This transformation is based on two sequential pathways: (i) Pd(ii)-mediated oxidation of the secondary alcohol to the corresponding ketone and (ii) Pd(0)/norbornene-catalyzed reaction of the in situ generated ortho-bromoacetophenone with the aryl iodide.

E-Olefins through intramolecular radical relocation

Full control over the selectivity of carbon-carbon double-bond migrations would enable access to stereochemically defined olefins that are central to the pharmaceutical, food, fragrance, materials, and petrochemical arenas. The vast majority of double-bond migrations investigated over the past 60 years capitalize on precious-metal hydrides that are frequently associated with reversible equilibria, hydrogen scrambling, incomplete E/Z stereoselection, and/or high cost. Here, we report a fundamentally different, radical-based approach. We showcase a nonprecious, reductant-free, and atom-economical nickel (Ni)^(I)-catalyzed intramolecular 1,3-hydrogen atom relocation to yield E-olefins within 3 hours at room temperature. Remote installations of E-olefins over extended distances are also demonstrated.