If you want efficiency and selectivity then 2 steps would be required.

I would recommend a Friedel Crafts acylation with the corresponding acyl chloride and AlCl3 in DCM. Followed by a Wolff-Kishner reduction.

You could also use NIS to convert the tetraphenylsilane into Iodobenzene, metallate and quench with the corresponding n-alkyl halide.

Dear Eric B. J. Harris, the Friedel Craft acylation can yield substitution of trimethylsilyl group to acyl group easily?

Yes, a silyl group directly activates a benzene ring for ipso substitution in the presence of an electrophile. The beta silicon effect significantly stablises the Wheland intermediate to the extent that ipso substitution should be exclusive in that system. The acylated product should be sufficiently deactivated not to react further and the corresponding acylium cations are less likely to rearrange.

Direct Friedel-Crafts alkylation would be preferable but has the added difficulties in that the alkylated species activates the benzene ring to further substitution and that primary carbocations tend to rearrange. It may be possible to do this under kinetic control at lower temperatures if ipso substitution has a lower activation energy than the two anticipated side reactions of product alkylation, and rearrangement of the reacting carbocation.

Dear Eric B. J. Harris

Thanks for your suggestion and providing nice explanation.