The Stereochemistry of Free-Radical Addition to Dienes. The Addition and Cooxidation of Thiols with Piperylene¹

Free-Radical Rearrangements

“…Thus, in the allylic chlorination of eis-and irarts-2-butenes with /-butyl hypochlorite at 40°C, the l-chloro-2-butenes are formed with complete retention of the cistrans stereochemistry (682). Other reactions are known in which allyl radicals suffer a partial loss of their cis-trans stereochemistry (685)(686)(687). On the other hand, in the reduction of eis-and frans-l-chloro-2-butenes with triphenyltin hyd ride at 80°C, the 2-butenes produced indicate that interconversion of the isomerie allylic radicals is competitive with hydrogen abstraction from the tin hydride (683,684).…”

Thiol‐Ene Radical Addition of L‐Cysteine Derivatives to Low Molecular Weight Polybutadiene

“…[16][17][18][19][20][21][22][23][24][25][26][27][28] Another remarkable mechanism aspect was a noticeable anti-Markovnikov behaviour of the addition reaction. [6,7,14,15,29,30] During the 1980s, Priola et al [27,28] obtained functionalised PBLs with 2-mercaptoethanol, TGA, 3-mercaptopropanoic acid or (mercaptopropyl)trimethoxy silane (MPTS) by using photoinitiators under UV lighting. Gorski and coworkers [19,24,25] used 8-mercaptooctan-1-ol or MPTS [24,25] with the same polymeric substrates to obtain a PB that, under particular conditions, could undergo a sol-gel process by creating a cross-linked resin.…”

The Main Mechanism and Cross-Linking Structure for Accelerated Sulfur Vulcanization

“…The addition of a free radical to the diene compound produces the allylic radical and results in several products of structural isomers [36][37][38][39][40][41][42][43][44][45] .…”

“…The radical addition of thiols to cis and trans diene compounds would be a good clue concerning the nature of allylic radicals. In the radical addition of thiol to 1,3pentadiene, the 1,2-and 1,4-adduct are mainly obtained by the attack of the thiyl radical at the C1 position of 1,3-pentadiene 44) . Then, the ratio of 1,2-and 1,4-adducts was similar to the radical stability of both secondary allylic radicals, as an intermediate ( Figure 3).…”

“…Study of the stereochemistry, also carried out by the radical addition of aromatic thiol to the cis and trans 1,3pentadiene, in the absence or presence of oxygen, gives both 1,2-and 1,4-adduct. Cis 1,3-pentadiene mainly gives cis 1,2-adduct and trans 1,3-pentadiene gives trans 1,2adduct with high stereospecificity ( Figure 6) 44,45) .…”