trans-1,4-Dibromo-2-butene → (4-Bromo-but-2-enyl)-(2,3-dihydro-benzo[1,4]dioxin-6-yl)-carbamic acid benzyl ester

Participants

Reaction Conditions

Reaction Steps

A solution of (2,3-dihydro-benzo[1,4]dioxin-6-yl)-carbamic acid benzyl ester (5 g, 17.5 mmol) in dry THF (85 mL) was cooled to −78° C. At this temperature n-BuLi (2.5M solution in hexanes, 14 mL) was added dropwise and the clear solution stirred at −78° C. for 20 min. A solution of E-1,4-dibromobut-2-ene (4.9 g, 23 mmol) in THF (42 mL) was added dropwise and the mixture slowly allowed to warm to rt. The mixture was poured on water and extracted with EA. The combined org. extracts were dried over MgSO4 and concentrated. The product was purified by FC (Hept/EA 9:1, 4:1) and obtained as a greenish oil (2.88 g, 38% yield) which was used as such in the next step despite some contaminations with starting material.

Provenance & Evidence