398
2
General Synthetic Methods
⊡ Scheme 36
⊡ Scheme 37
⊡ Scheme 38
5.2 Ring Expansions
The cyclopropane system is a tool for inserting a methylene unit into a ring system to form
a larger ring structure. Even densely functionalized pyranoids such as 161 [130,131] and cyclohexanes [132] expand into heptanoids and cycloheptanes, respectively. 1,2-C-dibromomethylene sugar 163 expands its pyranose ring to give oxepine 164 [133] ( > Scheme 39).
2
General Synthetic Methods
⊡ Scheme 36
⊡ Scheme 37
⊡ Scheme 38
5.2 Ring Expansions
The cyclopropane system is a tool for inserting a methylene unit into a ring system to form
a larger ring structure. Even densely functionalized pyranoids such as 161 [130,131] and cyclohexanes [132] expand into heptanoids and cycloheptanes, respectively. 1,2-C-dibromomethylene sugar 163 expands its pyranose ring to give oxepine 164 [133] ( > Scheme 39).