Asymmetric Synthesis of α-Methyl-α-Amino Acids via Diastereoselective Alkylation of (1S)-(+)-3-Carene Derived Tricyclic Iminolactone

Condensed Phase Kinetic Studies of Hydroxynitrates Derived from the Photooxidation of Carene, Limonene, trans-Carveol, and Perillic Alcohol

Organic hydroxynitrates (HNs) are key products of hydrocarbon oxidation in the atmosphere. Understanding the fate and processing of these molecules is critical due to their function in the sequestration of NOx species from the atmosphere and in the formation of secondary organic aerosol. However, the direct study of individual HNs’ reactivity has been largely hindered by the lack of authentic standards which has further limited the ability to deconvolute the role of structural features. Herein, we report the kinetic stabilities of six biogenic volatile organic compound-derived HN in acidified single-phase organic/water matrices. Lifetimes for tertiary HNs ranged from 15 min to 6.4 h, whereas secondary HN varied from 56 days to 2.1 years. Product analysis highlights the role that additional non-hydrolysis reactions have in the condensed phase conversion of HNs. This work provides the first evidence for the structural dependence of HN stability in bulk mixed media.

Copper-catalyzed intramolecular iminolactonization cyclization reactions of remote C(sp3)–H bonds in carboxamides

A novel and efficient synthetic method for iminolactones by copper-catalyzed intramolecular C(sp3)–H bond functionalization of carboxamides via a cascade process is reported for the first time.

Catalyst-Free Multicomponent Cyclopolymerizations of Diisocyanides, Activated Alkynes, and 1,4-Dibromo-2,3-Butanedione: a Facile Strategy toward Functional Polyiminofurans Containing Bromomethyl Groups

Polymers containing iminofuran (PIFs) are rarely reported due to the lack of simple and effective synthesis methods. In this work, a novel multicomponent cyclopolymerization (MCCP) of diisocyanides, activated alkynes, and 1,4-dibromo-2,3-butanedione using catalyst-free one-pot reactions under mild conditions to prepare PIFs containing bromomethyl groups is reported. PIFs with good solubility and thermal stability are obtained with high M_w s (up to 19 600) and good yields (up to 89.5%) under optimized polymerization conditions. The structure of the PIFs is characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy, and gel permeation chromatography. The photophysical properties indicate that polymers P1a2b3 and P1c2b3 have cluster-triggered emission characteristics. Thin films made from PIFs quickly degrade under UV irradiation. Moreover, the obtained polymers are decorated with bromomethyl and carboxylate groups in the side chain, which can be postfunctionalized to prepare multifunctional materials, such as star branched polymers and biomedical carrier materials. Thus, this work not only enriches the field of polymerization based on isocyanates and activated alkynes but also provides a facile strategy toward functional iminofuran polymers.

Enantioselective synthesis of cyclic quaternary α-amino acid derivatives by chiral phosphoric acid catalysis

A highly enantioselective aza-Friedel-Crafts reaction of N-sulfonyl cyclic ketimines with indoles catalyzed by chiral phosphoric acids has been developed. This methodology provides an efficient and facile route to indole-containing chiral cyclic α-amino acid derivatives bearing a quaternary stereocenter in high yields and up to 98% enantioselectivity.

Synthesis of quaternary α-methyl α-amino acids by asymmetric alkylation of pseudoephenamine alaninamide pivaldimine

The utility of pseudoephenamine as a chiral auxiliary for the alkylative construction of quaternary α-methyl α-amino acids is demonstrated. The method is notable for the high diastereoselectivities of the alkylation reactions, for its versatility with respect to electrophilic substrate partners, and for its mild hydrolysis conditions, which provide α-amino acids without salt contaminants. Alternatively, α-amino esters can be obtained by direct alcoholysis.

Potassium [1-(tert-but-oxy-carbon-yl)-1H-indol-3-yl]trifluoro-borate hemihydrate

The asymmetric unit of the title salt, K⁺·C₁₃H₁₄BF₃NO₂·0.5H₂O, consists of two derivatized indolyltrifluoridoborate anions, two potassium cations and one water mol­ecule. Within the indolyltrifluoro­borate anions, the least-square planes consisting of the carboxyl group and the adjacent quarternary C atom of the tert-butyl groups deviate significantly from coplanarity with the indolyl planes [20.44 (11) and 21.02 (10)°]. The potassium ions are coordinated by six atoms (one K⁺ ion by two O and four F atoms, and the second K⁺ ion by one O and five F atoms), however, one of the potassium ions undergoes an additional weak potassium–π inter­action (K⋯centroid = 3.722 Å). The packing is stabilized by sequential O—H⋯O hydrogen bonds along [100] between water mol­ecules and also by O—H⋯F hydrogen bonds.