Insertion into non-activated C(sp3)—H bonds: rapid construction of an added-value molecular diverse library

The selective functionalization of non-activated C(sp3)—H bonds within alkyl chains represents one of the major challenges in synthetic organic chemistry. 1-bromoalkynes, readily available from simple starting materials, may be transformed into a library of molecularly complex and diverse compounds by means of a well-defined intramolecular C(sp3)—H bond insertion reaction, using extremely simple reaction conditions. In addition, these compounds display a C—Br bond amenable for further functionalization. A preliminary mechanistic study supports a concerted [1,5]-H shift / C—C bond formation involving a gold-stabilized vinylcation-like transition state. The most salient feature of this methodology is the ability to functionalize in a predictable way non-activated C(sp3)—H bonds without any sort of electronic, geometric, or conformational bias.