The increasingly widespread applications of α,ω-dibromides motivated development of a scalable, inexpensive process to rapidly convert selected α,ω-alkanediols to the corresponding dibromides. Diols were heated with only 48% aq HBr and an organic solvent, using a Dean–Stark apparatus modified to fractionate the azeotropic distillate, thereby maintaining a higher HBr concentration and reaction rate in the pot. Intensified distillation also increased the reaction rate. Various other substrate, solvent, and parameter effects have been discovered and rationalized.

In response to the continuing widespread use of heterodifunctional C4 secondary methyl building blocks in asymmetric synthesis, we have developed a mole-scale, two-step synthesis of a 1:1 mixture of the diastereomers of 3-bromo-2-methyl-1-propyl camphorsulfonate (casylate). One isomer (2S) has been crystallized to >99:1 dr in ∼25% yield. Equilibration of the mother liquor (enriched in 2R) to a 1:1 mixture and recrystallization significantly raises the overall yield of 2S. Applications of 2S include chemoselective Grignard coupling, enabling the very short synthesis of highly stereopure long-chain natural products containing remote, methyl-bearing stereogenic centers [e.g., (R)-tuberculostearic acid], with complete control of configuration. Also, Ag-mediated, completely chemoselective Br displacement from 2S leads to a range of >99:1 er difunctional synthons. Both applications incorporate concurrent recovery of CasO. The enantiomer of 2S can be made from commercial (1R)-10-CasOH.