Publication

Sparteine-mediated a-lithiation of N-BOC-N-methylbenzylamine: Rapid racemization and subsequent deracemization

Manfred Schlosser
1995
Journal Articles

Abstract

Upon a-lithiation of N-BOC-N-methylbenzylamine (tert-Bu N-benzyl-N-methylcarbamate) with sec-BuLi in the presence of (-)-sparteine, the pro-(S) proton is preferentially abstracted (kinetic resoln. of the racemic a-deuterated deriv. up to 88% enantiomeric excess). The enantiomerically enriched organometallic intermediate thus generated instantaneously racemizes. Enantioselectivity, however, is restored in the course of 15-45 min., apparently due to adduct formation between the (S)-aminobenzyllithium species and sparteine. Subsequent reaction with typical electrophiles (CO2, CS2, MeI, Me2SO4, w-deuteriophenylacetylene) occurs with retention (51-90% enantiomeric excess), in hexane or Et2O, and with inversion (68-85%), in THF. [on SciFinder (R)]

Official source

https://infoscience.epfl.ch/entities/publication/a5e65e35-6f57-4e3c-8aa3-d1f3f9e515d4

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Manfred Schlosser
1995
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/a5e65e35-6f57-4e3c-8aa3-d1f3f9e515d4

About this result

Related concepts (18)

Organolithium reagent

In organometallic chemistry, organolithium reagents are chemical compounds that contain carbon–lithium (C–Li) bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom to the substrates in synthetic steps, through nucleophilic addition or simple deprotonation. Organolithium reagents are used in industry as an initiator for anionic polymerization, which leads to the production of various elastomers.

Extinction

Extinction is the termination of a taxon by the death of its last member. A taxon may become functionally extinct before the death of its last member if it loses the capacity to reproduce and recover. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the fossil record) after a period of apparent absence.

Species

In biology, a species (: species) is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour, or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined.