 As noted above , variants that deviate from this template are known ; what designates a Nazarov cyclization in particular is the generation of the pentadienyl cation followed by electrocyclic ring closure to an oxyallyl cation . In order to achieve this transformation , the molecule must be in the s @-@ trans / s @-@ trans conformation , placing the vinyl groups in an appropriate orientation . The propensity of the system to enter this conformation dramatically influences reaction rate , with α @-@ substituted substrates having an increased population of the requisite conformer due to allylic strain . Coordination of an electron donating α @-@ substituent by the catalyst can likewise increase the reaction rate by enforcing this conformation . 
