Positional selectivity of the methylation of 5-substituted tetrazolate anions

Abstract

The methylation of a series of 15 sodium 5-substituted tetrazolates using iodomethane in acetone/water (4 : 1) has been studied. The reaction yields both 1- and 2-methyl products, and the ratio of these products is discussed in terms of the nature of the 5-substituent. Electronic and steric effects dominate the reaction pathway; both increased substituent electro negativity and steric bulk lead to predominant methylation at N2. Sodium 5-ethoxycarbonyltetrazolate (3n) goes against this trend and an intermediate is proposed where the incoming electrophile is associated with the ester carbonyl group.

CHN7 – A Molecule Like Almost Solid Nitrogen

“…5-Azidotetrazole has been reported to be one of the strongest acids amongst 5-substituted tetrazole derivatives, due to the electron withdrawing properties of the azido-group (pseudohalide) [24]. For 5-substituted tetrazoles with electron withdrawing groups (such as halides (-Cl), pseudohalides (-CN, -CF 3 ) or classic electron withdrawing groups, such as -NO 2 , p-NO 2 -Ph-or -SO 2 Me) the N2 protonated tautomer is favored in solution, whereas tetrazoles with electron donor substituents in the 5-position such as -NH 2 or -CH 3 are protonated preferentially on N1 [25]. However, due to the minimal energetic differences between both tautomers, it is likely that both can exist, depending on the chemical environment and physical conditions: Temperature and solvent effects also influence the equilibrium between the 1H and 2H tautomers.…”

Fluorinated Triazoles and Tetrazoles

“…Also a direct halogenation was performed of the 5-trifl uoromethyltetrazole sodium salt with the molecular chlorine furnishing the N-chloroderivative of 5-trifl uoromethyltetrazole that was found an explosive extremely dangerous at handling [ 92 ]. The high regioselectivity of tetrazolate 97 alkylation in the environment of aqueous acetone giving predominantly the 2Н-isomer was later noted also by Spear et al [ 100 ]. 5-Trifl uoromethyltetrazole 96 slowly reacts with formaldehyde in water solution at pH 5 giving 2-hydroxymethyl-5-trifl uoromethyltetrazole 108 [ 101 ].…”

Azide Chemistry – An Inorganic Perspective, Part II[‡][3+2]‐Cycloaddition Reactions of Metal Azides and Related Systems

“…As a rule, a mixture of 1-and 2-substituted tetrazoles is formed, and a detailed study on the reaction of a series of 5-substituted sodium tetrazolates with iodomethane established that both, increased 5-substituent electronegativity and steric bulk lead to predominant methylation at N 2 . [318] (b) From tetrazolato metal complexes www.zaac.wiley-vch.de…”