Differentially substituted 1,3-diaryl-substituted allylic cations generated by ionization of the corresponding allylic alcohols in the presence of a Lewis acid undergo chemoselective and regioselective electrocyclization reactions to generate 1-aryl-1H-indenes. Electrocyclization only occurs for allylic cations bearing a 2-substituent, with 2-ester and 2-alkyl substituents both tolerated. In general, the presence of electron-withdrawing substituents deactivates the ring and disfavors cyclization. In contrast, the selectivity of cyclization of systems containing electron-donating substituents depends on the nature and position of the electron-donating group. Electron-donating substituents at the meta position particularly favor cyclization. There was no obvious correlation of cyclization selectivity with calculated electron densities as has been suggested for electrophilic aromatic substitution reactions. However, the calculated selectivities determined by a gas-phase (B3LYP/6-31G* + ZPVE) comparison of the relative rates of cyclization were in remarkably good agreement with the observed selectivities. Calculated transition-state structures for cyclization are consistent with a cationic pi4(a) conrotatory electrocyclization mechanism. In some cases involving more electron-deficient systems, the initially formed 1H-indene underwent subsequent alkene isomerization to the 3H-indene. In one example, an unusual dimerization reaction occurred to give a cyclopenta[a]indene via an unusual formal cationic 2pi+2pi cycloaddition of the allylic cation with the intermediate indene.

This article describes the rapid, green synthesis of a biaryl compound (4-phenylphenol) via a Pd(0)-catalyzed Suzuki cross-coupling reaction in water. Mild reaction conditions and operational simplicity makes this experiment especially amenable to both mid- and upper-level undergraduates. The methodology exposes students to purely aqueous microscale organic reactivity and showcases topical research in the milieu of an industrially applicable process.

Keywords: Amino acids / Amines / Transamination / Rearrangement / Chiral resolution Biomimetic studies of pyridoxal and pyridoxamine models are of both fundamental and practical interest. This review examines (i) deracemization of α-amino acids with a chiral pyridoxal model, (ii) sensing of chirality of small molecules including α-, β-, and γ-amino acids, peptides, amino alcohols and diamines with an achiral pyridoxal model and (iii) stereospecific synthesis of chiral diamines with a chiral pyridoxamine model. A binol-based aldehyde is useful as a chiral pyridoxal model to deracemize a variety of α-amino acids to make D-amino acids. 2,2Ј-Dihydroxybenzophenone is useful

A microscale organic synthesis experiment is outlined where students undertake both a "traditional" and "modern" Biginelli preparation of a dihydropyrimidone, within the same three-hour session. Each method is straightforward, appropriate as part of a mid-level undergraduate laboratory, and performed individually or between a pair of students. Emphasis is placed on comparing approaches from a green chemistry perspective. The class probes concepts of catalytic reactivity, solvent-free synthesis, atom economy, and energy consumption to assess green improvements made by employing the modern strategy.

Hammett plot reveals that there is a significant electronic effect on the rate of resonance assisted hydrogen bond (RAHB) directed diaza-Cope rearrangement reaction with a rho value of 1.6. DFT computation shows that the rearrangement reaction becomes thermodynamically more favorable for the substrates with electron withdrawing substituents. A substrate with the nitro substituent (1a) reacts about 50-fold faster than that with the methoxy substituent (1g).