126497-25-4Relevant academic research and scientific papers
Cyclohexynes as intermediates in a novel endo-cyclization of alkynylzincates derived from 5-hexynyl tosylates
Harada, Toshiro,Otani, Takeshi,Oku, Akira
, p. 2855 - 2858 (1997)
The n-type endo-cyclization of metal acetylides to form cyclohexynes was observed for the first time in the reaction of alkynylzincates derived from 5-hexynyl tosylates. The endo-cyclization took place in competition with erocyclization, leading to the formation of 1-(cyclopentylidene)alkylzincs.
Cyclization of acetylenic alkyllithiums
Bailey, William F.,Ovaska, Timo V.
, p. 3080 - 3090 (2007/10/02)
The scope and limitations of cyclization reactions involving acetylenic alkyllithiums, which were prepared at-78 °C by lithium-iodine exchange between the corresponding iodide and tert-butyllithium in a solution of n-pentane-diethyl ether (3:2 by volume), have been investigated. 4-Pentynyllithiums, 5-hexynyllithiums, and 6-heptynyllithiums bearing a phenyl or trimethylsilyl substituent on the triple bond undergo regiospecific exo-dig cyclization to give 4-, 5-, and 6-membered rings, respectively, bearing an exocyclic lithiomethylene moiety. Cyclization of the analogous alkyl-substituted acetylenic alkyllithiums seems to be confined to the 5-exo mode. The vinyllithium products of the cyclizations may be trapped by reaction with electrophiles to afford functionalized cycloalkylidene derivatives in good yield. The cyclization reactions were found to be highly stereoselective: intramolecular addition of the C-Li unit to the triple bond to produce 4- or 5-membered rings proceeds in a syn fashion to generate isomerically pure exocyclic vinyllithiums that may be functionalized to give stereoisomerically pure products. At the higher temperatures needed to effect cyclization of 6-heptynyllithiums, the initially formed (Z)-vinyllithium intermediate is isomerized to the more stable E-isomer which, when trapped with an electrophile, affords stereoisomerically pure product formally derived from anti addition to the triple bond.
PREPARATION AND FACILE CYCLIZATION OF 5-ALKYN-1-YLLITHIUMS
Bailey, William F.,Ovaska, Timo V.,Leipert, Thomas K.
, p. 3901 - 3904 (2007/10/02)
Primary 5-hexyn-1-yllithiums, which may be generated in virtually quantitative yield by low-temperature lithium-iodine interchange, undergo regiospecific 5-exo-dig cyclization via stereoselectively syn-addition of CH2Li to the alkyne moiety to give vinyllithiums that may be trapped with any of a variety of electrophiles to deliver functionalized cyclopentylidene-containing products.
