[79791-38-1; 119652-78-7] · C18H29N3O2S · p-Dodecylbenzenesulfonyl Azide · (MW 351.57)
(diazo-transfer reagent for activated methylene groups1)
Alternate Name: p-DBSA.
Physical Data: liquid mixture of isomers without precise mp or bp.
Solubility: sol pentane, acetone, and most organic solvents.
Form Supplied in: viscous liquid.
Analysis of Reagent Purity: elemental analysis (C, H, N, S) and HPLC.
Preparative Method: prepared by addition of granular Sodium Azide (1.3 equiv) to a mixture of isomeric sulfonyl chlorides (from a commercial mixture of isomers of p-dodecylbenzenesulfonic acid) in acetone solution.1
Purification: elution through short column containing silica gel G with methylene chloride-hexane (1:4) as eluant.1
Handling, Storage, and Precautions: is the safest of the usual arenesulfonyl azides (tosyl azide, etc.) employed in diazo-transfer processes;1 appropriate care should be taken, as with all azides. Use in a fume hood.
The title reagent has been called a safer diazo-transfer reagent, and is a mixture of 12 or more isomeric p-dodecylbenzenesulfonyl azides, ranging by HPLC from 24% to 1% in area and giving essentially a single spot by TLC.1
The title reagent has been shown to be very useful for the synthesis of various crystalline diazocarbonyl compounds such as diazobarbituric and diazoisopropylidenemalonic acids,1 derivatives and homologs of diazoacetoacetic acid,1,2 and 9-diazoanthrone (eq 1).1
Formation of noncrystalline byproduct dodecylsulfonamides facilitates the workup procedure and isolation of the target crystalline diazo compounds from the reaction mixture.1
Vinyldiazomethanes containing two electron-withdrawing groups are readily available using p-DBSA in the presence of Triethylamine (eq 2).3
The process seems to be nonstereospecific. From a mixture of diethyl cis- and trans-glutaconates, exclusively the trans-diazo compound was isolated in high yield, indicating that equilibration occurs under the reaction conditions.3
The reagent is also effective in the case of allyl methyl ketone, which has a less acidic methylene group than the previous substrate (eq 3).4
The reaction is complete in a few minutes but a stronger base, 1,8-Diazabicyclo[5.4.0]undec-7-ene, is required for initial anion formation.
Valerij A. Nikolaev
St. Petersburg State University, Russia