Chapter 2 Electrophile-induced 5-endo cyclizations

摘要: Publisher Summary This chapter presents a review on electrophile-induced 5- endo cyclizations of unsaturated alcohol, amine and thiol derivatives when induced by various electrophiles, predominantly iodine selenides. One the fundamental tenets Baldwin's rules cyclization is that -trig processes are particularly disfavored. Therefore, during studies iodolactonizations ( E )-3-silyloxyalk-5-enoic acids, it was discovered small amounts ca . 5%) iodotetrahydrofurylacetic acids were also formed. observation accompanied finding such led largely to trans -3,5-disubstituted valerolactones, presumably via chair conformation, wherein silyloxy group held in an axial position hydrogen bonding with carboxylic acid. The discusses (1) -iodocyclizations homoallylic alcohols, (2) selenocyclization (3) pyrrolidine formation using 5-endo-trig cyclizations, (4) sulfur as nucleophile, (5) -dig cyclizations. Most types (E)-homoallylic alcohols undergo smooth stereoselective give excellent yields iodotetrahydrofurans. A conceptually different approach asymmetric synthesis tetrahydrofurans employ chiral, non-racemic selenium reagent. Endo distinguished from foregoing two contrasting ways: firstly, these favored according but, secondly, have enjoyed significantly less popularity.