High Regiocontrol in the Zinc-Mediated Crotylation of Aldehydes and Ketones: A Straightforward and Facile Approach to Linear Homoallylic Alcohols in DMPU

The α‐regioselectivity of carbonyl crotylation is a long‐standing problem in the realm of C–C bond formation reactions. We demonstrate that zinc‐mediated crotylation of aldehydes and ketones can afford α‐linear homoallylic alcohols exclusively to provide a simple solution for this problem. In this context, we describe a method for the α‐regioselective crotylation of aldehydes and ketones by using an easily available starting material, such as crotyl bromide, zinc dust, and the less‐toxic solvent DMPU. The reaction has broad substrate scope and is highly efficient. Moreover, a metallo‐[3,5]‐sigmatropic rearrangement is proposed to account for the high α‐regioselectivity in the zinc‐mediated crotylation. The α‐regioselective addition of crotyl bromide to carbonyl compounds was realized by the use of convenient and inexpensive zinc as the mediator with broad substrate scope in an environmentally benign solvent. Good to high yields of the corresponding α‐linear homoallylic alcohols were obtained with perfect α‐regioselectivity.