NOVELTY - Preparation of ticagrelor (I) involves: reacting, 2-(((3aR,4S,6R,6aS)-6-amino-2,2-dimethyltetrahydro-3aH-cyclopenta(d)(1,3)-dioxol-4-yl)oxy)-1-ethanol or its salt (i) with 4,6-dichloro-2-(propylthio)-5-pyrimidinamine (ii) or its salt in a solvent and base in presence of catalyst to obtain 2-(((3aR,4S,6R,6aS)-6-((5-amino-6-chloro-2-(propylthio)-4-pyrimidinyl)amino)-2,2-dimethyltetrahydro-3aH-cyclopenta(d)(1,3)dioxol-4-yl)oxy)-1-ethanol (iii), and optionally isolating the compound (iii), followed by diazotizing, condensing, deprotecting, isolating and purifying steps.    USE - For preparation of ticagrelor (claimed) which is used as as an adenosine uptake inhibitor, platelet aggregation inhibitor, P2Y12 purinoceptor antagonist and coagulation inhibitor drug, used for the prevention and treatment of thrombosis, angina, ischemic heart diseases, and coronary artery diseases.    ADVANTAGE - The method results less than 0.20% of (1S,2S,3R,5S)-3-(7-(((1R,2S)-2-(3,4-diflurophenyl)-cyclopropyl) amino)-5-(propylthio)-3H-(1,2,3)triazolo(4,5-d) pyrimidin-3-yl)- 5-(oxyethylacetate)-1,2-cyclopentanediol. The method eliminates the impurities formed during the preparation of the compound (I); is economic, efficient, eco-friendly and eliminates extensive laborious work-up; is simple, easy and user friendly; is free from impurities, thus eliminating the required purification steps and further making the process cost effective and efficient.    DETAILED DESCRIPTION - Preparation of ticagrelor of formula (I) involves: a) reacting, 2-(((3aR,4S,6R,6aS)-6-amino-2,2-dimethyltetrahydro-3aH-cyclopenta(d)(1,3)-dioxol-4-yl)oxy)-1-ethanol or its salt of formula (i) with 4,6-dichloro-2-(propylthio)-5-pyrimidinamine of formula (ii) or its salt in a solvent and base in presence of a catalyst to obtain 2-(((3aR,4S,6R,6aS)-6-((5-amino-6-chloro-2-(propylthio)-4-pyrimidinyl)amino)-2,2-dimethyltetrahydro-3aH-cyclopenta(d)(1,3)dioxol-4-yl)oxy)-1-ethanol of formula (iii), and optionally isolating the compound (iii); b) reacting the compound (iii) with a diazotizing agent in an acid and a solvent to prepare 2-(((3aR,4S,6R,6aS)-6-(7-chloro-5-(propylthio)-3H-(1,2,3)triazolo(4,5-d)pyrimidin-3-yl)-2,2-dimethyltetrahydro-3aH-cyclopenta(d)(1,3)dioxal-4-yl)oxy)-1-ethanol compound of formula (iv); c) reacting the compound (iv) with trans-(1R,2S)-2-(3,4- difluorophenyl) cyclopropanamine or its salt of formula (v) in a solvent, a base, and optionally in presence of a catalyst to produce 2-(((3aR,4S,6R,6aS)-6-(7-(((1R,2S)-2-(3,4-diflurophenyl)-cyclopropyl)amino)-5-(propylthio)-3H-(1,2,3)triazolo(4,5-d)pyrimidin-3-yl)-2,2-dimethyltetrahydro-3aH-cyclopenta(d)(1,3)dioxal-4-yl)oxy)-1-ethanol of formula (vi); d) deprotecting the compound (vi) using aqueous acid in a solvent to obtain ticagrelor of formula (I), and isolating the compound (I); e) purifying ticagrel (I). An INDEPENDENT CLAIM is included for new 2-(((3aR,4S,6R,6aS)-6-((5-amino-6-chloro-2-(propylthio)-4-pyrimidinyl)amino)-2,2-dimethyltetrahydro-3aH-cyclopenta(d)(1,3)dioxol-4-yl)oxy)-1-ethanol (iii) which is crystalline in nature and is confirmed by X-ray diffraction (XRD) pattern as shown in figure 1 of the specification.