Alkynediols, hydroalkoxylation

An iridium(m) hydride catalyzed intramolecular alkyne hydroalkoxylation can be used to construct isochromans 545 bearing a C(3)-spiroacetal moiety (Equation 226) <2005OL5437>. Novel isochromans bearing an array of C(3)-spiroacetal moieties are accessible via the hydroboration of alkynediols with disiamylborane followed by treatment of the resulting alkenylboron compounds with alkaline hydrogen peroxide <1998CL81>. 

Mercury(II) triflate has emerged as an effective catalyst for a variety of cycli-zations [108], Its use in the hydroalkoxylation of alkynediols has been investigated by Deslongchamps and coworkers [109] (Scheme 45). 

Scheme 15 Rh(I) catalyzed double intramolecular hydroalkoxylation of alkynediols...

The same catalyst was used for the double intramolecular hydroalkoxylation reaction for the synthesis of a series of spiroacetals starting from internal and terminal alkynediols [32] (Scheme 15). 

---