Superbasic mix  BuLi+tert-BuOK is well known and readily available :

Schlosser, M. (1988). "Superbases for organic synthesis". Pure Appl. Chem. 60 (11): 1627–1634. doi:10.1351/pac198860111627

Mix of tert-BuLi + tert-BuOCs should be more stronger

http://jmortier.unblog.fr/directed-metalation-chemistry/

What solvent are you doing it in, the temperature sounds quite high?

BuLi decomposes above 50oC.

Ziegler, K.; Gellert, H. G. Liebigs Ann. Chem. 1950, 567, 179.

Firstly, Thank you all for the answers provided.

We are doing the reaction in dry hexane(68 degrees bp) but, we are able to reflux only after 76 degrees. @Patricck Killoran 

As we are using TMEDA to the BuLi, it forms an adduct and hence probably that won't decompose at 50 degrees. Also, we performed the same reaction at same conditions with Thiophene instead of DTP. It worked out pretty well. We were able to get 80% yield. @Eugene Yang

I'll try  tert-BuLi + tert-BuOCs. Thank you @Andrei Rogoza 

You can try halide metal exchange reaction of alkyl lithiun with other alkyl bromide.

You have to carry out lithiation only below 0 degree with lithio bases .You can try DME as the solvent with sec.BuLi or LDA at -78 degree.

Dear 

can you opt for t-Buli but then no need to heat at 55 °C execute at - 78 C