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 In organic chemistry, the diazo group is an organic moiety consisting of two linked nitrogen atoms at the terminal position. Overall charge-neutral organic compounds containing the diazo group bound to a carbon atom are called diazo compounds ...

compound (notably

diazomethane Diazomethane is an organic chemical compound with the formula 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 ga ...

) and a dipolarophile. When the dipolarphile is an

alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

, the reaction product is a

pyrazoline Pyrazoline is a heterocyclic A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic organic chemistry is the branch of organic chemistry dea ...

. The reaction product of a cycloaddition between

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

regioselective In organic 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 str ...

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 acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

. The reaction is also a syn addition, 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 o ...

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 carr ...

of the 2-pyrazoline to the

pyrazole Pyrazole is an organic compound with the chemical formula, formula . It is a heterocycle characterized as an azole with a 5-membered ring of three carbon atoms and two adjacent nitrogen atoms, which are in Arene substitution pattern, ortho-substi ...

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

References

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