Divergent Elementoboration: 1,3‐Haloboration versus 1,1‐Carboboration of Propargyl Esters

This work showcases the 1,3‐haloboration reaction of alkynes in which boron and chlorine add to propargyl systems in a proposed sequential oxazoliumborate formation with subsequent ring‐opening and chloride migration. In addition, the functionalization of these propargyl esters with dimethyl groups...

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Bibliographic Details
Published in:Chemistry : a European journal 2018-05, Vol.24 (29), p.7364-7368
Main Authors: Wilkins, Lewis C., Soltani, Yashar, Lawson, James R., Slater, Ben, Melen, Rebecca L.
Format: Article
Language:English
Subjects:
Alkynes
boranes
Boron
Chelates
Chemistry
Chlorine
Communication
Communications
Density functional theory
Esters
haloboration
Lewis acid
Migration
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Summary:This work showcases the 1,3‐haloboration reaction of alkynes in which boron and chlorine add to propargyl systems in a proposed sequential oxazoliumborate formation with subsequent ring‐opening and chloride migration. In addition, the functionalization of these propargyl esters with dimethyl groups in the propargylic position leads to stark differences in reactivity whereby a formal 1,1‐carboboration prevails to give the 2,2‐dichloro‐3,4‐dihydrodioxaborinine products as an intramolecular chelate. Density functional theory calculations are used to rationalize the distinct carboboration and haloboration pathways. Significantly, this method represents a metal‐free route to highly functionalized compounds in a single step to give structurally complex products. The 1,3‐haloboration reaction of alkynes are described within whereby boron and chlorine add to propargyl systems in a proposed sequential trans‐oxyboration with subsequent ring‐opening and chloride migration. In addition, the simple derivatization of these propargyl esters with dimethyl groups in the propargylic position leads to a formal 1,1‐carboboration to give the 2,2‐dichloro‐3,4‐dihydrodioxaborinine products as an intramolecular chelate. This method represents a metal‐free route to highly functionalized compounds in a single atom‐economic step to give structurally diverse products.
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201801493