Isocyclics octanes

Butyn-2-one undergoes tandem [3+2] cycloadditions of allyltriisopropylsilane to give a bicyclo[3.3.0]octane as a mixture of three possible diastereomers in a good yield (Scheme 10.169) [468]. The use of a reduced amount of the allylsilane forms a silylated cyclopentene as a minor product. This indicates that the 1 1 cycloadduct is the precursor of the bicyclic product. In contrast, the ZnL or Me2AlCl-promoted reaction of 3-butyn-2-one with an isocyclic allyltrimethylsilane affords a [2+2] adduct wifhout [3+2] adducts [448a, 469] (vide infra). 

Bicyclo[2.2.2]octanes can be obtained by a simple method The synthesis of the griseofulvin system has been accomplished in essentially one operation by a double Michael addition to an ethynyl vinyl ketone The sesquiterpenes longifolene with its highly intricate skeleton, and caryophyllene have yielded to ingenious synthetic endeavors. Cyclobutene ring closures by photoisomerization of conjugated dienes are used for the construction of various isocyclic and heterocyclic systems... 

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