- Photoinitiated Thiol-Ene “Click” Reaction: An Organocatalytic Alternative
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The thiol-ene coupling (TEC) reaction has attracted a lot of scientific attention during the last years, particularly in the fields of polymers, materials and more recently in drug design. The combination of organocatalysis and photocatalysis has enabled the development of an efficient synergistic protocol for the addition of various thiols to a plethora of olefins. Utilizing phenylglyoxylic acid as the catalyst-initiator and common household bulbs as the light source, we report an organocatalytic photoinitiated TEC reaction showing exceptional tolerance in the presence of various functionalities, untangling previously unsolved problems. (Figure presented.).
- Limnios, Dimitris,Kokotos, Christoforos G.
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supporting information
p. 323 - 328
(2017/02/05)
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- Visible light photocatalysis with benzophenone for radical thiol-ene reactions
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We report herein a simple, metal- and oxidant-free visible light promoted strategy for an anti-Markovnikov hydrothiolation of unactivated olefins using benzophenone as an inexpensive photocatalyst at room temperature. Anti-Markovnikov adducts of a wide va
- Singh, Manjula,Yadav, Arvind K.,Yadav, Lal Dhar S.,Singh
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supporting information
p. 2206 - 2208
(2017/05/16)
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- Transition metal photoredox catalysis of radical thiol-ene reactions
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We describe the anti-Markovnikov hydrothiolation of olefins using visible-light-absorbing transition metal photocatalysts. The key thiyl radical intermediates are generated upon quenching of photoexcited Ru*(bpz) 32 with a variety of thiols. The adducts of a wide variety of olefins and thiols are formed in excellent yield (73-99%).
- Tyson, Elizabeth L.,Ament, Michael S.,Yoon, Tehshik P.
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p. 2046 - 2050
(2013/03/29)
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- Enantioselective synthesis, configurational stability, and reactivity of lithium α-tert-butylsulfonyl carbanion salts
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The reactions of enantiopure S-tert-butyl sulfones of the type R 1CH(R2)SO2tBu (≥99% ee) with lithiumorganyl compounds gave the corresponding chiral α-sulfonyl carbanion salts [R 1C(R2)SO2tBu]Li with ≥94% ee. The enantioselectivity of the deprotonation of the phenyl- but not dialkyl-substituted sulfones is strongly dependent on the nature of the lithiumorganyl. Because of this observation and the strong decrease in enantioselectivity in the presence of TMEDA and HMPA, we propose an intramolecular proton transfer following complexation of the sulfone by RLi. Racemization of [R1C(R2)-SO2tBu]Li follows first-order kinetics and seems to be mainly an enthalpic process with a small negative activation entropy, as revealed by polarimetric measurements at low temperatures. This is in accordance with Cα-S bond rotation as the rate-determining step. The salts [R1C(R2)SO 2tBu]Li have half-lives of racemization in the order of several hours at -105°C. The deuteriation of the salts at -105°C with CF 3CO2D proceeded with enantioselectivities of 94% ee, the magnitude of which was not significantly affected by the presence of TMEDA and HMPA. The salts also reacted with carbon-based electrophiles at low temperatures with high enantioselectivity. The conversion of R1CH(R 2)SO2tBu via [R1C(R2)SO 2tBu]Li to R1C(R2,E)SO2tBu, which involves the loss of stereogenicity at the α-stereogenic center and its reestablishment upon reaction of the chiral carbanion with electrophiles, occurred with high overall enantioselectivity. Electrophiles attack the anionic C atom of [R1C(R2)SO2tBu]Li with high selectivity on the side syn to the O atoms and anti to the tert-butyl group. The reactivity of the dialkyl-substituted salts [R1C(R 2)SO2tBu]Li (R1, R2 = alkyl) is significantly higher than that of the benzylic salts [RC(Ph)SO2tBu]Li (R = alkyl) and the HMPA-coordinated SIPs of [MeC(Ph)SO2- tBu]Li are significantly more reactive towards EtI than the corresponding O-Li contact ion pairs.
- Scholz, Roland,Hellmann, Gunther,Rohs, Susanne,Oezdemir, Diana,Raabe, Gerhard,Vermeeren, Cornelia,Gais, Hans-Joachim
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supporting information; experimental part
p. 4588 - 4616
(2010/10/21)
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- Montmorillonite K 10-catalyzed regioselective addition of thiols and thiobenzoic acids onto olefins: An efficient synthesis of dithiocarboxylic esters
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The addition of thiols and thiobenzoic acids onto olefins proceeded regioselectively in a Markovnikov manner in the presence of Montmorillonite K 10 (Mont K 10) clay as the catalyst to afford thioethers and thiocarboxylic S-esters, while high selectivity to anti-Markovnikov products was realized in the absence of any catalyst. Treatment of the esters with Lawesson's reagent provided the corresponding dithiocarboxylic esters in high yields.
- Kanagasabapathy, Subbareddy,Sudalai, Arumugam,Benicewicz, Brian C.
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p. 3791 - 3794
(2007/10/03)
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