1-cyclopropyl-1-alkene 1-alkyne

Cyclopropyl arenes, alkynes and ALKENES from the IN srru GENERATION OF B CYCLOPROPYL 9 BBN AND THE SUZUKI-MIYAURA COUPLING OF ARYL, ALKYNYL AND ALKENYL BROMIDES... 

The double hydroboration of propargyl bromide with 9-borabicyclo[3.3.1]nonane (9-BBN-H) proceeds smoothly to afford the corresponding l,l-diboryl-3-bromo-propane adduct which is quantitatively converted to the B-hydroxy-B-cyclopropyl-9-BBN and / /3-hydroxy-9B BN complexes in equal molar amounts. Addition of this mixture to aryl, alkynyl and alkenyl bromides containing a catalytic (3%) amount of Pd[PPh3]4, after 8-16 hours at reflux temperature, provides the corresponding cyclopropylated arenes, alkynes and alkenes in good to excellent yields.111... 

Additional evidence for the involvement of metal carbenes in these processes was obtained in the reaction of dimeric substrates with a cationic Au(I) catalyst to give disubstituted alkynes (equation 39). These reactions can be explained by isomerization of the initially formed cyclopropyl gold carbene by a [1,3] metallotropic shift, followed by intramolecular trapping of the gold carbene by the alkene. Other examples of [1,3] metallotropic shifts in gold chemistry have been observed recently. ... 

In this 3-phcnylalkyne system the triple bond becomes incorporated into a cyclo-propene ring, whereas from the enynes 10 and 11 there is no sign of a vinylcyclo-propene product. The preference for reaction to take place at the alkene unit rather than at the alkyne unit in the photochemistry of enynes is seen again in the photochemistry of enepoly-yne chlorides, where only cyclopropyl chlorides are produced (equation 18). This preference is probably a reflection of the lower strain energy in a cyclopropane than in a cyclopropene ring. 

Catalytic codimerizations between cyclopropenes and alkenes (or alkynes) to give four-membered rings have only been achieved with 3,3-dimethyl- and 3-cyclopropyl-3-methylcyclopropene on the one hand and norbomene or norbomadiene on the other (stereochemistry not determined)77> ... 

The formation of substituted cyclopropane rings by the reaction of alkenes with Fischer carbenes has been known for some time [58]. More recently, cyclopropyl groups have been produced as parts of bicyclic and tricyclic ring systems by, formally, the reaction of Fischer carbenes with one equivalent of alkene and one equivalent of alkyne. Indeed, this reaction type proceeds through alkene trapping of a metal carbene generated in situ. The various methodologies that have been developed may be divided into three classes the intermolecular reaction of a,co-enynes with Fischer carbenes, the partially intramolecular reaction of Fischer carbene-tethered alkynes with alkenes, and the fully intramolecular reactions of Fischer carbene-tethered enynes. No fiilly intramolecular version of this reaction has been reported. 

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