in my opinion new land lord occupies the same position as the lessor  :AIR1915CAL64(66)DB AND AIR 1950 PUNJAB Iis authority in this regard confirmation of lease from new land lord / agreement between newland lord and lesee may be taken .

When lessor sold his interests to others, the new lessor or old lessor shall give notice to lessee. Till then if any rent payed to old lessor is due payment. After getting notice lessee shall pay rent to new owner. There is no law imposing restriction to sell land upon owner. There is no preferential rights under any law for tenants to insist upon landlord to sell to him. However it is a debatable question. 

what is the condition write in document otherwise lessor give a notice to lessee for vacant the premises.

or the lessee paid a rent to the new purchaser.

this condition apply :-

ATTORNMENT

The Lessor specifically agrees and undertakes that in the event the leased premises are sold, transferred, mortgaged or conveyed to any third party by the Lessor, such transfer shall be subject to the terms of this Lease Deed and the Lessee shall continue to be in possession of the leased premises without any interruption or disturbance by the transferee.

The transfer is subject to the tenancy only. If the transfree of the property asks the tenant to pay the rent to him, the later has to pay. If the transfree do not whisper in this regard, then the tenant haxs to give a notice to the transfree attorning to the later.