[41294-30-8] · C5H9Br2Li · 1,1-Dibromopentyllithium · (MW 235.88)
(used in conjunction with n-butyllithium for homologation of carbonyl compounds1)
Solubility: sol ether, THF.
Preparative Method: prepared by the reaction of 1,1,1-tribromopentane with butyllithium in THF-ether at -100 °C.1
Handling, Storage, and Precautions: stable only at very low temperature (-100 °C); cannot be stored.
1,1-Dibromo-1-pentyllithium adds readily to aldehydes or ketones. In the presence of a second equiv of n-Butyllithium, a further lithium carbenoid2,3 can be generated which undergoes a rearrangement in which a preferential migration of a hydrogen over an organic group is observed (eq 1). After hydrolysis, a mixture of two isomeric carbonyl compounds is observed (eqs 2 and 3). In some cases, only one rearrangement product is produced (eq 4)1. The reaction can be extended to other 1,1-dibromides (eq 5),1 as well as to the performance of ring expansions (eq 6).1 The related homologation of esters using Dibromomethyllithium has been extensively investigated.4
Philipps-Universität, Marburg, Germany