Metalated Thioether, Selenoether, and Ether

A companion reagent to the ylide is the corresponding metalated sulfide 30 which arises by the lithiation of 29 with n-butyllithium 66). The latter forms by base closure of 28. Since closure of 28 b involves use of n-butyllithium, the cyclopropyl sulfide 29 simply becomes an intermediate which is metalated in situ to give 30 directly67. A non-metalation sequence involves 32 which undergoes reductive 

Similar methods also generate the selenium and oxygen analogues 33 0 and 34 71), respectively, as outlined in Eq. 37 and 38. These organolithium species add to carbonyl groups of non-conjugated and conjugated aldehydes and ketones, frequently 

Entry Aldehyde 1 or ketone Reagent Adduct (% Yield) Rearrangement method Cyclobutanone (% Yield) Ref. 

Cyclopropylcarbinyl-cyclobutyl ring expansions (Eq. 5) are facilitated by the presence of the heteroatom substituent in the order O S Se. In this case, the heteroatom stabilized cyclobutyl cation (see Eq. 39) can suffer hydrolysis to give the 

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