The Diazoalkane 1,3-dipolar cycloaddition is a 1,3-dipolar cycloaddition (an organic reaction) between a

1,3-dipole In organic chemistry, a 1,3-dipolar compound or 1,3-dipole is a dipolar compound with delocalized electrons and a separation of charge over three atoms. They are reactants in 1,3-dipolar cycloadditions. The dipole has at least one resonance st ...

diazo The diazo group is an organic moiety consisting of two linked nitrogen atoms ( azo) at the terminal position. Overall charge neutral organic compounds containing the diazo group bound to a carbon atom are called diazo compounds or diazoalkanes ...

compound (notably

diazomethane Diazomethane is the chemical compound CH2N2, discovered by German chemist Hans von Pechmann in 1894. It is the simplest diazo compound. In the pure form at room temperature, it is an extremely sensitive explosive yellow gas; thus, it is almos ...

) and a dipolarophile. When the dipolarphile is an

alkene In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

, the reaction product is a

pyrazoline Pyrazoline is a heterocyclic chemical compound with the molecular formula C3H6N2. {{heterocyclic-stub ...

. The reaction product of a cycloaddition between

and trans-diethyl glutaconate is a 1-pyrazoline. This reaction is 100%

regioselective In chemistry, regioselectivity is the preference of chemical bonding or breaking in one direction over all other possible directions. It can often apply to which of many possible positions a reagent will affect, such as which proton a strong ba ...

because the diazo terminal nitrogen atom bonds exclusively to the alpha-carbon of the

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ...

. The reaction is also a

syn addition In organic chemistry, syn- and anti-addition are different ways in which substituent molecules can be added to an alkene or alkyne. The concepts of syn and anti addition are used to characterize the different reactions of organic chemistry by refl ...

, and the configuration in the dipolarophile is preserved. The 1-pyrazoline is unstable and isomerizes to the 2-pyrazoline due to favorable

conjugation Conjugation or conjugate may refer to: Linguistics *Grammatical conjugation, the modification of a verb from its basic form * Emotive conjugation or Russell's conjugation, the use of loaded language Mathematics *Complex conjugation, the change ...

with the

group. With diazo(phenyl)methane as the reactant the regioselectivity is reversed and the reaction is extended even further by simple air

organic oxidation Organic reductions or organic oxidations or organic redox reactions are redox reactions that take place with organic compounds. In organic chemistry oxidations and reductions are different from ordinary redox reactions, because many reactions car ...

of the 2-pyrazoline to the

pyrazole Pyrazole is an organic compound with the formula C3H3N2H. It is a heterocycle characterized by a 5-membered ring of three carbon atoms and two adjacent nitrogen atoms, which are in ortho-substitution. Pyrazole is a weak base, with p''K''b 11.5 ( ...

Another example of a diazo cycloaddition is a diazo-thioketone coupling.

References

{{DEFAULTSORT:Diazoalkane 1,3-Dipolar Cycloaddition Cycloadditions Heterocycle forming reactions