Publications de Christophe Heiss

Remote trimethylsilyl groups interfering with the ortho deprotonation of fluoroarenes and chloroarenes

(2-Fluorophenyl)trimethylsilane (2-F) and (2-chlorophenyl)trimethylsilane (2-Cl) react with sec-butyllithium or lithium 2,2,6,6-tetramethylpiperidide under permutational hydrogen/metal interconversion (metalation) more slowly than, resp., the corresponding ...

2007

Trifluoromethyl-substituted phenylsilanes: the regiochemical course of their metalation dictated by buttressing effects

Christophe Heiss

Triethyl[(2-trifluoromethyl)phenyl]silane reacts with the superbasic LIC-KOR mixt. of butyllithium and potassium tert-butoxide exclusively at the 4-position ("meta-metalation") and not at all at the 3-position ("ortho-metalation"). Two further substrates w ...

2006

Relay propagation of crowding: the trifluoromethyl group as both an emitter and transmitter of steric pressure

Fabrice Cottet, Rosario Scopelliti, Christophe Heiss, Eric Masson

Whereas lithium 2,2,6,6-tetramethylpiperidide (LITMP) abstrs. a proton exclusively from the 4-position of 3-bromobenzotrifluoride, the same base attacks selectively the 2-position when employed in the presence of N,N,N',N'',N''-pentamethyldiethylenetriamin ...

2006

Proton mobility in 2-substituted 1,3-dichlorobenzenes: "ortho" or "meta" metalation?

Rosario Scopelliti, Christophe Heiss

Nine 1,3-dichlorobenzene congeners were selected as model compds. to assess the relative rates of proton abstraction from 4- and 5-positions ("ortho" vs. "meta" metalation). Using lithium 2,2,6,6-tetramethylpiperidide as the basic reagent, the chlorine-adj ...

2006

Fluorine-flanked congested sites: Minimal, though perceptible buttressing effects on the proton mobility of arenes

Christophe Heiss

(2,6-Difluorophenyl)trimethylsilane, -triethylsilane and -triisopropylsilane undergo sec-butyllithium-mediated metalation at the 3- and 4-position (ortho and meta relative to the halogen) in ratios of 99.6:0.4, 98:2 and 95:5, resp. The steric pressure tran ...

2005

Meta- rather than ortho-directed metalations: Buttressing effects prejudicing the proton abstraction from (2,6-dihalophenyl)silanes

Fabrice Cottet, Christophe Heiss

(2,6-Dichlorophenyl)trimethyl- and -triethylsilane exhibit untypical reactivity patterns toward strong bases. When treated at -100 DegC with lithium 2,2,6,6-tetramethylpiperidide, they give rise to two, with sec- or tert-butyllithium even three, different ...

2005

Buttressing effects responsible for the meta-deprotonation of trialkylsilyl-substituted haloarenes by organometallic reagents : an unprecedented phenomenon

Christophe Heiss

(2,6-Dichlorophenyl)trimethyl- and triethylsilane exhibit untypical reactivity patterns toward strong bases: when treated at -100 °C with lithium 2,2,6,6-tetramethylpiperidide two, with sec- or tert-butyllithium even three organometallic intermediates are ...

EPFL2005

Promoting or preventing haloaryllithium isomerizations: differential basicities and solvent effects as the crucial variables

Thierry Rausis, Christophe Heiss

Deprotonation-triggered heavy halogen migrations should become a favorite tool in arene synthesis if their occurrence and outcome could be made predictable. Particularly attractive, though extremely rare, are stop-and-go situations where a first intermedia ...

Georg Thieme Verlag2005