NOVELTY - Preparing 2-(trans-4-(4'-chlorophenyl)cyclohexyl)-3-hydroxy-1,4-naphthoquinone (atovaquone) (I), comprises e.g. ketone brominating cis/trans mixture of 2-(4-(4-chlorophenyl)cyclohexyl)-3,4-dihydronaphthalen-1(2H)-one (VI) to obtain cis/trans mixture of 2-bromo-2-(4-(4-chlorophenyl)cyclohexyl)-3,4-dihydronaphthalen-1(2H)-one (VII); eliminating (VII) with strong base to give cis/trans mixture of 2-(4-(4-chlorophenyl)cyclohexyl)naphthalene-1-ol (VIII) and followed by oxidizing, base catalyzed epoxidation and acid catalyzed hydrolysis.    USE - The process is useful for preparing atovaquone, which is useful in the treatment of pneumocystis carinii pneumonia, malaria, toxoplasmosis, carcinoma or fibrosarcoma. No biological data given.    ADVANTAGE - The process is cost effective, operation friendly, green and eco-friendly process for preparing atovaquone, without separating any diastereomers or geometric isomers of intermediates obtained during the reactions.    DETAILED DESCRIPTION - Preparing 2-(trans-4-(4'-chlorophenyl)cyclohexyl)-3-hydroxy-1,4-naphthoquinone (atovaquone) (I), comprises: (a) condensing (1,2-dihydronaphthalen-4-yloxy)trimethylsilane (II) with 4-(4-chlorophenyl)cyclohexanone (III) in presence of Lewis acid in organic solvent to obtain 2-(4-(4-chlorophenyl)-1-hydroxycyclohexyl)-3,4-dihydronaphthalen-1(2H)-one (IV); (b) dehydrating (IV) in organic solvent and in presence of acid comprising para-toluene sulfonic acid to obtain diastereomeric mixture of 2-(4-(4-chlorophenyl)cyclohex-1-enyl)-3,4-dihydronaphthalen-1(2H)-one (V); (c) hydrogenating (V) with platinum dioxide to obtain cis/trans mixture of 2-(4-(4-chlorophenyl)cyclohexyl)-3,4-dihydronaphthalen-1(2H)-one (VI); (d) optional selectively crystallizing (VI) to separate the cis and trans isomers of 2-(4-(4-chlorophenyl)cyclohexyl)-3,4-dihydronaphthalen-1(2H)-one; (e) ketone brominating (VI) to obtain cis/trans mixture of 2-bromo-2-(4-(4-chlorophenyl)cyclohexyl)-3,4-dihydronaphthalen-1(2H)-one (VII); (f) in absence of optional selectively crystallizing (VI), optional selectively crystallizing (VII) to separate the cis and trans isomers of (VII); (g) eliminating (VII) with strong base to give cis/trans mixture of 2-(4-(4-chlorophenyl)cyclohexyl)naphthalene-1-ol (VIII); (h) in absence of optional selectively crystallizing (VII), optionally crystallizing (VIII) to separate the cis and trans isomers of (VIII); (i) oxidizing cis/trans mixture of (VIII) to obtain cis/trans mixture of 2-(4-(4-chlorophenyl)cyclohexyl)naphthalene-1,4-dione (IX); (j) base catalyzed epoxidation of cis/trans mixture of (IX) to cis/trans mixture of 1a-(4-(4-chlorophenyl)cyclohexyl)naphtho(2,3-b)oxirene-2,7(1aH,7aH)-dione (X) in presence of hydrogen peroxide; and (k) acid catalyzed hydrolysis of (X) to obtain (I). INDEPENDENT CLAIMS are also included for:    (1) 2-(4-(4-chlorophenyl)-1-hydroxycyclohexyl)-3,4-dihydronaphthalen-1(2H)-one (IV);    (2) preparing (IV), comprising step (a) as per se;    (3) 2-(4-(4-chlorophenyl)cyclohex-1-enyl)-3,4-dihydronaphthalen-1(2H)-one (V);    (4) (1,2-dihydronaphthalen-4-yloxy)trimethylsilane (II);    (5) 4-(4-chlorophenyl)cyclohexanone (III);    (6) 2-(4-(4-chlorophenyl)cyclohexyl)-3,4-dihydronaphthalen-1(2H)-one (VI);    (7) 2-bromo-2-(4-(4-chlorophenyl)cyclohexyl)-3,4-dihydronaphthalen-1(2H)-one (VII);    (8) 2-(4-(4-chlorophenyl)cyclohexyl)naphthalene-1-ol (VIII);    (9) 2-(4-(4-chlorophenyl)cyclohexyl)naphthalene-1,4-dione (IX);    (10) 1a-(4-(4-chlorophenyl)cyclohexyl)naphto(2,3-b)oxirene-2,7(1aH,7aH)-dione (X);    (11) preparing (III), comprising preparing (4-chlorophenyl)magnesium bromide (a1) (Grignard reagent) by reacting 1-bromo-4-chlorobenzene with magnesium turning in presence of catalytic amount of iodine, reacting (a1) with 1,4-cyclohexanedione monoethylene ketal to obtain 8-(4-chlorophenyl)-1,4-dioxa-spiro(4.5)decan-8-ol) (a2), dehydrating (a2) in toluene and in presence of p-toluene sulfonic acid and ethylene glycol to obtain 4-(4-chlorophenyl)-cyclohex-3-enone monoethylene ketal (a4), hydrogenating (a4) in presence of noble metal catalyst comprising palladium on carbon, platinum oxide to obtain 4-(4-chlorophenyl)-cyclohexanone monoethylene ketal (a5) and deketalization of (a5) in presence of para-toluene sulfonic acid in mixture of acetone and water to obtain (III);    (12) preparing cis isomer (XIV) of atovaquone, comprising converting cis-2-(4-(4-chlorophenyl)cyclohexyl)naphthalene-1-ol (XI) to cis-4-(4-chlorophenyl)cyclohexyl)naphthalene-1,4-dione (XII) in presence of sulfuric acid/sodium nitrite, sodium bromate/acetic acid, acetic acid/hydrogen peroxide or ruthenium chloride/hydrogen peroxide/acetic acid, converting (XII) to cis-1a-(4-(4-chlorophenyl)cyclohexyl)naphtha(2,3-b)oxirene-2,7(1aH,7aH)-dione (XIII) in presence of hydrogen peroxide and sodium bicarbonate and converting (XIII) to (XIV) in presence of sulfuric acid; and    (13) isomerization of cis isomer of atovaquone to trans-atovaquone in presence of Lewis acid.