Unusual addition by the thiol-ene photopolymerization

Synthesis of New Lipid‐Inspired Ionic Liquids by Thiol‐ene Chemistry: Profound Solvent Effect on Reaction Pathway

“…adds onto the less substituted ene carbon, generating a stabilized C‐centered radical intermediate 7. However, Klemm and Bell reported a so called “unusual” Markovnikov‐oriented addition of dithiols across the alkenes through the electrophilic addition of thiols 8…”

“…Clearly, the "kinked" structure of its C 18 tail is highly effective to bring about depression in the Further, correlation spectroscopy (COSY) and heteronuclear single-quantum correlation spectroscopy (HSQC) data confirm unequivocally the structures of branched ILs. In addition to NMR data, the ESI-MS fragmentation patterns of branched ILs showed the common cleavage of the CÀS bond of the longest chain [11] with retention of charge on the ring and sulfur containing fragments and formation of stable or [MeIm(CH 2 ) nÀ2 -(CHCH 3 )S] + C or [MeIm(CH 2 ) n S] + C radical cation for internallybranched (5-7) and externally-branched (8)(9)(10)(11) ILs, respective-ly. However, no evidence for decomposition products of linear analogues 1-4 were observed (Figure 1 c).…”

“…[7] However, Klemm and Bell reported a so called "unusual" Markovnikov-oriented addition of dithiols across the alkenes through the electrophilic addition of thiols. [8] Lipid-inspired ionic liquids (ILs), first described in our recent publications, [9] are a new class of biomaterials that utilize struc-tural features similar to natural lipids to allow the incorporation of lipophilic structural elements while keeping their melting points below room temperature. It has been observed for several homologous series of 1-n-alkyl-3-methylimidazolium salts that as the n-alkyl side chain increases in length above seven carbons, the melting points begin to rise dramatically, resulting in species that are room-temperature solids.…”

“…As shown in Scheme 2, the ILs comprising set A are alike in incorporating linear 18-atom side chains, but differ in the positions of the sulfur atom (1-4). Sets B and C are similarly formatted with respect to their side chains containing internal (5-7) or external (8)(9)(10)(11) methyl branches towards the cationic ring and located adjacent to sulfur atoms and were prepared exclusively in a Markovnikov fashion (Scheme 2). Most likely, due to the severe steric hindrance between the bulky cationic ring and in proximity to methyl substituent at C3 position, internally branched 3[Me]-4[S] IL did not form through the Markovnikovoriented path 1 in set B.…”