Preparation of Oxocanes by Electrophilic Cyclizations of Unsaturated Alcohols in the Presence of Bis(collidine)halonium(I) Hexafluorophosphates

Abstract

Keywords: Alcohols / Cyclic ethers / Cyclizations / Entropy / Medium-sized rings / Synthetic methods 7-Octen-1-ols substituted in the sp 3 −sp 3 carbon chain with carbocyclic (phenyl and cyclopropane) and heterocyclic (epoxide and dioxolane) moieties were prepared and their cyclizations in the presence of bis(collidine)iodonium(I) and -bromonium(I) hexafluorophosphates as electrophiles were studied. Oxocanes were obtained in modest to good yields when a rigid cyclic moiety (cyclopropane or phenyl) was present in the chain, while yields of cyclizations were lower if

2,6‐Disubstituted Tetrahydropyrans by Tandem Cross‐Metathesis/Iodocyclisation

“…Unlike compound 11 , the endo attack is not observed as a partial positive charge on the terminal site of the olefin would not be stabilised. The exclusive formation of the exo cycloadduct from terminal hydroxy alkenes has been reported with similar substrates21,24a and for the synthesis of oxepanes25 (7‐ exo vs. 8‐ endo ) and oxocanes28 (8‐ exo vs. 9‐ endo ).…”

Stereoselective Halogenation in Natural Product Synthesis

“…[74] This process was inefficient even using a crude preparation of bromoperoxidase enzyme(s) from Laurencia , which is thought to be responsible for such bond constructions in nature; however, that datum does not necessarily indicate that such transformations are poorly effective in the organism (Scheme 42). [75] …”

Recent Advances in the Synthesis and Reactivity of Vinylcyclopropanes

“…Rousseau and co-workers explored the iodocyclization of unsaturated alcohols, with VCP 218 the reaction gives cyclic iodo ethers 219 and 220. 82 With VCP alcohols as substrates, the reaction follows two pathways. One involves the double bond to give a [3,8]-fused iodo ether 219.…”