The mechanism and kinetics of thiol-maleimide "click" reactions carried out under a variety of conditions have been investigated computationally and using experimental competition reactions. The influence of three different solvents (chloroform, ethane thiol, and N,N-dimethylformamide), five different initiators (ethylamine, diethylamine, triethylamine, diazabicyclo[2.2.2]octane, and dimethylphenyl-phosphine), and seven different thiols (methyl mercaptan, β-mercaptoethanol, thioacetic acid, methyl thioglycolate, methyl 3-mercaptopropionate, cysteine methyl ester, and thiophenol) on the energetics and kinetics of thiol-maleimide reactions have been examined using density functional methods. Computational and kinetic modeling indicate that the choice of solvent, initiator, and thiol directly influences whether product formation follows a base-, nucleophile-, or ion pair-initiated mechanism (or some combination thereof). The type of mechanism followed determines the overall thiol-maleimide reaction kinetics. Insights from computational studies are then used to understand the selectivity of ternary thiol-maleimide reactions between N-methyl maleimide, 6 states were confirmed by IRC calculations and were distinguished as having a single imaginary vibrational frequency. All potential energy surface scans, geometry optimizations, and single-point calculations were performed at 298.15 K, 1.0 atm pressure, and in a PCM solvent model 24 for chloroform, ethyl mercaptan, or N,N-dimethylformamide.Theoretical investigations of methane thiolate additions to N-allyl and N-propargyl maleimide have been carried out previously 25 using the compound CBS-QB3 method developed by Petersson and co workers, 26 and results were found to agree well with experimental observations. Similarly, computational investigations of radical-initiated thiol-ene reactions have been carried out 14 at the CBS-QB3 level and were found to predict reaction enthalpies within ±0.5 kcal/mol mean absolute deviation (MAD) of experimental data. The number of heavy atoms present in large initiators (e.g. DBU, PMe 2 Ph) and thiols (e.g. thiophenol) investigated in the current study render these systems unsuitable for study at the CBS-QB3 level. Recent computational investigations by Houk 27 and Qi 28 have found that a combination of geometry optimizations at the B3LYP/6-31+G(D) level 22 followed by single-point energy calculations using Truhlar's MO6-2X functional 21 with a large basis set provide thiol-Michael reaction energetics that are in good agreement with CBS-QB3 benchmarks. All reaction and transition state enthalpies and free energies reported herein were obtained at the MO6-2X/6-311G(2D,P)//B3LYP/6-31+G(D) level of theory. Results and Discussion.Et 3 N-initiated mechanism in chloroform. The Et 3 N-initiated addition of methyl mercaptan (1) to NMM in CHCl 3 was chosen as a starting point for investigating the energetics, kinetics, and mechanism of thiol-maleimide reactions. As discussed above thiol-maleimide reactions are ideally suited to display rapid re...

We describe the synthesis of allyl-substituted deoxybenzoin-based aromatic polyesters that combine the advantageous thermal properties of deoxybenzoin with the processability and reactivity of pendent unsaturated groups. A thermally induced Claisen rearrangement of bis-allyl ether-substituted deoxybenzoin 2 produced 3,3′-bis-allyl-4,4′-bishydroxy­deoxybenzoin (BA-BHDB, compound 1) as a novel A2 monomer. BA-BHDB 1 polymerized readily with isophthaloyl chloride to produce a novel set of functional aromatic polyesters. These allyl-substituted polymers exhibited marked solubility advantages over deoxybenzoin-based polymers lacking such pendent groups, affording homogeneous solutions in numerous organic solvents. The processability contributed by the allyl groups afforded access to relatively high molecular weight aromatic polyesters, with estimated number-average molecular weight (M n) values exceeding 20 kDa. Interestingly, evaluation of the thermal properties of these polymers revealed that the pendent allyl groups led to small increases in heat release relative to the unsubstituted deoxybenzoin polymers. Thus, this work represents an advantageous design of nonflammable polymer materials, offering benefits with respect to both processability and heat release properties. Moreover, the utility of these functional deoxybenzoins in post-polymerization cross-linking was demonstrated using multifunctional thiols and thiol–ene reactions.

Base-catalyzed thiol-maleimide click chemistry has been applied to the synthesis of neutral donor-acceptor [2]rotaxanes in good yield. This method is extended further to the synthesis of a glutathione-functionalized [2]pseudorotaxane, a precursor to integrated conjugates of interlocked molecules with proteins and enzymes.

New, smart droplets can pick up nanoparticles from substrates.