In this work we used density functional theory (DFT) B3LYP/6-31G*(d) to study the stoichiometric reaction between the β-himachalene and dibromocarbene. We have shown that β-himachalene behaves as a nucleophile, while dibromocarbene behaves as an electrophile; that the chemical potential of dibromocarbene is superior to that of β-himachalene in absolute terms; and that β-himachalene reacts with an equivalent quantity of dibromocarbene to produce only one products P1: (1S,3R,8S) -2,2- dibromo -3,7,7,10

The reaction between α-trans-himachalene and dichlorocarbene has been studied using density functional theory (DFT) B3LYP/6-311G (d, p). The global electrophilicity and global nucleophilicity indices indicate that α-trans-himachalene behaves as a nucleophile while dichlorocarbene behaves as an electrophile. The majority product obtained by stoichiometric reaction between dichlorocarbene and α-trans-himachalene is (1R, 2S, 4R, 7S)-3,3-dichloro-8-methylene-4,12,12-trimethyl-tricyclo [5.5.0.02,4] dodecane (referred to here as P1(α)): in this reaction the attack takes place at the endocyclic double bond at the α side of α-trans-himachalene. The majority product obtained by the reaction between two equivalents of dichlorocarbene with α-trans-himachalene is (1R, 2S, 4R, 7S, 8R)-3,3,13,13-tetrachloro-4,12,12-trimethyl-tricyclo [5.5.0.02,4] -spiro[28] tetradecane (referred to here as P2(β)): here the attack takes place at the β side of the exocyclic double bond. P2(β) is also obtained by the equimolar reaction of P1(α) with dichlorocarbene. P1(α) and P2(β) are both exothermic. Analysis of local electrophilicity and local nucleophilicity indices demonstrates the chemo-, regio- and stereoselectivity of the reaction. Analysis of the potential energy surface shows that this reaction follows an asynchronous concerted mechanism. Calculating the intrinsic reaction coordinate (IRC) shows that the reaction mechanism can be characterized as "one-step" and "two-stage". Stationary points were characterized by frequency calculations in order to verify that the transition states had one and only one imaginary frequency.