Intramolecular site-selective insertion

When the cyclobutenone 33 was treated with a rhodium catalyst, the C(arene) -C(carbonyl) bond was site-selectively cleaved and the alkene moiety was intramolecularly inserted therein to construct the tetracyclic skeleton of 34. The isopropyl group was introduced by electrophilic aromatic bromination. 

The number of trial sites at any given step, km, can be chosen freely (k = 1 corresponds to an unbiased insertion) and should thus be optimized to improve efficiency [38]. For chain molecules with intramolecular potentials (e.g., bond bending and dihedral potentials), it is more convenient to divide the energy into a bonded part and a nonbonded part. The bonded part can then be used to efficiently bias the selection of trial positions and only the nonbonded part is used for the selection of trial sites and the calculation of the Rosenbluth weights [34,35,37]. Using an isolated chain with intramolecular interactions as the reference state, the excess chemical potential can now be obtained from... 

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