tosyl bromide (p-toluene sulfonyl bromide, prepared as described Page 18)
AIBN (azoisobutyronitrile) recrystallised from methanol from crude.
toluene, (anhydrous from CaH₂ or dry from Aldrich)
Wang-linked 5-hexenoic acid (prepared as for SP: 88)

p-Toluenesulfonyl bromide (6eq, 0.6mmol, 142mg) and AIBN (6eq, 0.6mmol, 98mg) were pre-dissolved in dry toluene (_{1ml) and added to polystyrene resin-linked 5-hexenoic acid (1eq, 0.1mmol, 0.72mmol/g, 139mg). The reaction was performed in a 3ml Reactivial^TM at 65-70^oC with stirring for 20h and allowed to cool to room temperature. The resin was then transferred to a filter tube and washed with DCM, DMF, THF 6 x 10mL each; 3 x 10mL each of DMSO, glacial acetic acid, 20% DIPEA/DMF. Final washes in THF. Cleaved with} 3ml 95% TFA(aq) for 2.5 hours. Washed through with DCM and THF and dried under stream of nitrogen and then overnight in vacuum oven at 30^oC. Yield: 32.5mg, 93%, colourless oil.

This reaction has been repeated about 4 times on this scale only, with yields consistently high for this Wang polystyrene-linked alkene acceptor. We did have problems associated with the removal of some tosyl-related impurities that did not wash off the resin and were only released by the TFA cleavage step. This problem was overcome by washing the resin with 20% DIPEA/DMF as descibed above. Prolonged washing in these basic conditions did lead to trace amounts of the elimination product so keep the washes to < 1min in the basic solution. The washes with DMSO and acetic acid were probably a bit excessive and unnecessary. The reaction vessels used: Reactivials^TM, are available from Pierce Warriner and are a good choice when doing small scale solid phase reactions that require heating since the resin is concentrated in one small volume and is relatively easy to transfer to an Alltech^TM tube for washing steps. See links to other synthetic pages below for how to make tosyl bromide and other related chemistry.

¹H NMR (MeOD) (300MHz) delta (ppm): 7.86 (d, J=8Hz, 2H, Ts H2 & H6), 7.50 (d, J=8Hz, 2H, Ts H3 & H5), 4.30-4.36 (m, 1H, H5), 3.85 (app. d, J=6.0Hz, 2H, H6+H6'), 2.50 (s, 3H, CH₃-Ar), 2.32 (m, 2H, H2), 2.08-2.16 (m, 1H, H4/H4'), 1.82-1.94 (m, 2H, H3/H3' + H4/H4'), 1.67-1.74 (m, 1H, H3/H3'). ¹³C NMR (MeOD): 177.2, 147.2, 138.2, 131.6, 129.8, 64.7, 46.5, 39.0, 34.2, 24.0, 22.1. MS (ES⁺) [M]⁺ 349, 347.

1. Caddick, S.; Hamza, D.; Wadman, S.N. Tetrahedron Lett. 1999, 40, 7285-7288.

Linking acceptor to solid support: Page 88; Solution phase addition of TsBr to alkynes Page 48; Preparation of Tosyl Bromide: Page 18. Addition of tosyl bromide and tosyl iodide to allenes see: Suk-Ku Kang, Byung-Soo Ko, and Young-Hwan Ha, J. Org. Chem., 2001; 66(10); 3630-3633.