This work focuses on the use of a gem-dithiolato-bridged rhodium(I) [Rh2(μ-S2CBn2)(cod)2] complex (cod = 1,5-cyclooctadiene, Bn2CS2 2- = 1,3-diphenyl-2,2-dithiolatopropane) dissolved in toluene in the presence of monodentate phosphite P-donor ligand (P(OPh)3) under carbon monoxide/hydrogen (1:1, syngas) atmosphere as an effective catalyst for hydroformylation of some olefins (oxo-reactions). The capability of this system to catalyze the hydroformylation of hex-1-ene, cyclohexene, 2,3-dimethyl-but-1-ene and 2-methyl-pent-2-ene and their quaternary mixture (synthetic naphtha) has been demonstrated. This innovative method to perform the in situ hydroformylation of the olefins present in naphthas to oxygenated products would be a promissory work for a future industrial catalytic process applicable to gasoline improving based on oxo-reactions. An important observation is that variation of CO/H2 pressure (6.8 - 34.0 atm), temperature (60 - 80 °C), reaction time (2 - 10 h), rhodium concentration ((1.0 - 1.8)x10-3 mol/L) affect hydroformylation reaction rates. Optimal conversion to oxygenated products were achieved under [Rh] = 1.8 x10-2 mol/L, P(CO/H2) = 34 atm (CO/H2 = 1:1) at 80 °C for 10 h.