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5424573 
Journal Article 
A Convenient Route to 2-Bromo-3-chloronorbornadiene and 2,3-Dibromonorbornadiene 
Lennartson, A; Quant, M; Moth-Poulsen, K 
2015 
1 
Synlett
ISSN: 0936-5214
EISSN: 1437-2096 
26 
11 
1501-1504 
WOS:000356859200014 
Substituted norbornadienes are useful in a wide range of applications, including molecular solar-thermal (MOST) energy storage systems. An important precursor for 2,3-substituted norbornadienes is 2-bromo-3-chloronorbornadiene, where the two halogen atoms can be substituted selectively through two consecutive Suzuki cross-coupling reactions. Previous routes to 2-bromo-3-chloronorbornadiene have used 1,2-dibromoethane as a brominating agent, a substance known to be carcinogenic and the use of which is restricted in certain countries. Herein is reported a one-pot route to 2-bromo-3-chloronorbornadiene in 50% yield using p-toluenesulfonyl bromide as a bromine source. In addition, the procedure has been adapted to allow synthesis of 2,3-dibromonorbornadiene in 37% yield. 
bromine; chlorine; organometallic reagents; regioselectivity; alkenes