Relative reactivity of substituted alkenes toward 1,3-dipoles

Terminal alkene — 0.89 (heptene) 0.15 (heptene) 2.6 (hexene) 0.072 (heptene) 

An interesting variation of the 1,3-dipolar cycloadditions involves generation of 1,3-dipoles from stable strained-ring compounds. As an example, aziridines 1 and 2 give adducts apparently derived from the reaction of 1,3-dipoles 3 and 4, respectively, with a variety of dipolarophiles. The evidence for the involvement of dipoles 

Cyclopropanones are also reactive toward cycloadditions of various types. It is suspected that a dipolar species resulting from reversible cleavage of the cyclo- 

Among the cycloaddition reactions that have been shown to have some generality and synthetic utility are the 2 + 2 cycloadditions of ketenes with alkenes. These 

Cyclobutanes can also be formed by noncerted reactions involving dipolar intermediates. Enamines react with certain electron-deficient alkenes to give cy- 

---

Table 6.1. Relative Reactivity of Substituted Alkenes toward 1,3-Dipoles ... 

---