A theoretical study of the mechanism and selectivity of [1+2] cycloaddition reactions between a-cis-himachalene and dichlorocarbene was performed using DFT B3LYP/6-311+G(d, p). Analysis of the global electrophilicity indeces shows that a-cis-himachalene behaves as a nucleophile, while dichlorocarbene behaves as an electrophile. In line with the local philicity concept, we propose a multiphilic descriptor. This descriptor is capable of simultaneously explaining the nucleophilicity and electrophilicity of the atomic sites in the molecule. The double bond of the six-membered ring is attacked when stoichiometric quantities of a-cis-himachalene and dichlorocarbene are used, while the other double bond is attacked by dichlorocarbene only when it is used in excess. The calculation of activation and reaction energies indicates that the a cycloadducts are favored both kinetically and thermodynamically