Publication

Hetero-atom effects on kinetic acidities: the metalation of 1-methylcyclohexene and its 4-aza- and 4-oxa-analogs

Manfred Schlosser
1985
Journal Articles

Résumé

Hexane suspensions of Me3SiCH2K or BuLi/Me3COK deprotonated 1-methylcyclohexene almost exclusively at the Me group. In contrast 1,4-dimethyl-1,2,3,6-tetrahydropyridine and 4-methyl-5,6-dihydro-2H-pyran preferentially underwent H/metal-exchange at the N-distant and oxygen-adjacent allylic methylene groups, resp. Strong amide bases converted 5,6-dihydro-2H-pyrans into (Z)-pentadienols. The mechanism of the latter ring-opening is discussed. [on SciFinder (R)]

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Manfred Schlosser
1985
Journal Articles

Résumé

Source officielle

Concepts associés (17)

Persistent carbene

A persistent carbene (also known as stable carbene) is a type of carbene demonstrating particular stability. The best-known examples and by far largest subgroup are the N-heterocyclic carbenes (NHC) (sometimes called Arduengo carbenes), for example diaminocarbenes with the general formula (R2N)2C:, where the four R moieties are typically alkyl and aryl groups. The groups can be linked to give heterocyclic carbenes, such as those derived from imidazole, imidazoline, thiazole or triazole.

Cheletropic reaction

In organic chemistry, cheletropic reactions, also known as chelotropic reactions, are a type of pericyclic reaction (a chemical reaction that involves a transition state with a cyclic array of atoms and an associated cyclic array of interacting orbitals). Specifically, cheletropic reactions are a subclass of cycloadditions. The key distinguishing feature of cheletropic reactions is that on one of the reagents, both new bonds are being made to the same atom. In the pericyclic transition state, a small molecule donates two electrons to the ring.

Metal–halogen exchange

In organometallic chemistry, metal–halogen exchange is a fundamental reaction that converts an organic halide into an organometallic product. The reaction commonly involves the use of electropositive metals (Li, Na, Mg) and organochlorides, bromides, and iodides. Particularly well-developed is the use of metal–halogen exchange for the preparation of organolithium compounds. Two kinds of lithium–halogen exchange can be considered: reactions involving organolithium compounds and reactions involving lithium metal.

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