NOVELTY - Preparation of apremilast involves reacting (1S)-1-(3-((1S)-1-((E)-((3-ethoxy-4-methoxyphenyl)methylidene)amino)ethyl)naphthalen-1-yl)ethan-1-amine with dimethyl sulfone, de-protecting obtained (1S)-1-(3-((1S)-1-((E)-((3-ethoxy-4-methoxyphenyl)methylidene)amino)ethyl)naphthalen-1-yl)ethan-1-amine using a de-protecting agent, obtaining 1-(3-ethoxy-4-methoxyphenyl)-2-methanesulfonylethan-1-amine (III), reacting 1-(3-ethoxy-4-methoxyphenyl)-2-methanesulfonylethan-1-amine with N-(1,3-dioxo-1,3-dihydro-2-benzofuran-4-yl)acetamide (II), and obtaining apremilast.    USE - Preparation of apremilast used for treating inflammatory disease e.g. arthritis, osteoarthritis, rheumatoid arthritis, and psoriatic arthritis, inflammatory bowel disease e.g. Crohn's disease and ulcerative colitis, sepsis, psoriasis, atopic dermatitis, contact dermatitis, chronic obstructive pulmonary disease, and chronic inflammatory pulmonary disease.    ADVANTAGE - The method enables efficient preparation of apremilast, by economical and environmentally-friendly process.    DETAILED DESCRIPTION - Preparation of apremilast comprises reacting 3-ethoxy-4-methoxybenzaldehyde of formula (VII) and (1S)-1-(naphthalen-1-yl)ethan-1-amine of formula (VI), obtaining (1S)-1-(3-((1S)-1-((E)-((3-ethoxy-4-methoxyphenyl)methylidene)amino)ethyl)naphthalen-1-yl)ethan-1-amine of formula (V), reacting (1S)-1-(3-((1S)-1-((E)-((3-ethoxy-4-methoxyphenyl)methylidene)amino)ethyl)naphthalen-1-yl)ethan-1-amine with dimethyl sulfone, obtaining (1S)-1-(3-((1S)-1-((1-(3-ethoxy-4-methoxyphenyl)-2-methanesulfonylethyl)amino)ethyl)naphthalen-1-yl)ethan-1-amine of formula (IV), de-protecting (1S)-1-(3-((1S)-1-((E)-((3-ethoxy-4-methoxyphenyl)methylidene)amino)ethyl)naphthalen-1-yl)ethan-1-amine using a de-protecting agent, obtaining 1-(3-ethoxy-4-methoxyphenyl)-2-methanesulfonylethan-1-amine of formula (III), reacting 1-(3-ethoxy-4-methoxyphenyl)-2-methanesulfonylethan-1-amine with N-(1,3-dioxo-1,3-dihydro-2-benzofuran-4-yl)acetamide of formula (II), and obtaining apremilast.    INDEPENDENT CLAIMS are also included for:    (1) preparation of apremilast which comprises reacting 1-(3-ethoxy-4-methoxyphenyl)-2-methanesulfonylethan-1-amine with 3-nitrophthalic anhydride, obtaining 2-((1S)-1-(3-ethoxy-4-methoxyphenyl)-2-methanesulfonylethyl)-4-nitro-2,3-dihydro-1H-isoindole-1,3-dione, reducing 2-((1S)-1-(3-ethoxy-4-methoxyphenyl)-2-methanesulfonylethyl)-4-nitro-2,3-dihydro-1H-isoindole-1,3-dione using reducing agent, obtaining 4-amino-2-((1S)-1-(3-ethoxy-4-methoxyphenyl)-2-methanesulfonylethyl)-2,3-dihydro-1H-isoindole-1,3-dione, and acetylating 4-amino-2-((1S)-1-(3-ethoxy-4-methoxyphenyl)-2-methanesulfonylethyl)-2,3-dihydro-1H-isoindole-1,3-dione with acetylating agent;    (2) preparation of apremilast which comprises providing (Z)-(1-(3-ethoxy-4-methoxyphenyl)-2-(methylsulfanyl)ethylidene)(1-(naphthalen-2-yl)ethyl)amine, de-protecting (Z)-(1-(3-ethoxy-4-methoxyphenyl)-2-(methylsulfanyl)ethylidene)(1-(naphthalen-2-yl)ethyl)amine with de-protecting agent, obtaining 1-(3-ethoxy-4-methoxyphenyl)-2-(methylsulfanyl)ethan-1-amine, reacting 1-(3-ethoxy-4-methoxyphenyl)-2-(methylsulfanyl)ethan-1-amine with N-(1,3-dioxo-1,3-dihydro-2-benzofuran-4-yl)acetamide, obtaining N-(2-((1S)-1-(3-ethoxy-4-methoxyphenyl)-2-(methylsulfanyl)ethyl)-1,3-dioxo-2,3-dihydro-1H-isoindol-4-yl)acetamide, and oxidizing N-(2-((1S)-1-(3-ethoxy-4-methoxyphenyl)-2-(methylsulfanyl)ethyl)-1,3-dioxo-2,3-dihydro-1H-isoindol-4-yl)acetamide with an oxidizing agent;    (3) preparation of apremilast which comprises reacting 3-nitrophthalic acid with reducing agent, obtaining 3-aminophthalic acid, reacting 3-aminophthalic acid with acetic anhydride, reacting 2-ethoxy-4-isocyano-1-methoxybenzene with N-(1,3-dioxo-1,3-dihydro-2-benzofuran-4-yl)acetamide with resolving agent, and obtaining N-(1,3-dioxo-1,3-dihydro-2-benzofuran-4-yl)acetamide compound of formula (XIV), and    (4) intermediate chosen from 2-((1S)-1-(3-ethoxy-4-methoxyphenyl)-2-methanesulfonylethyl)-4-nitro-2,3-dihydro-1H-isoindole-1,3-dione, 4-amino-2-((1S)-1-(3-ethoxy-4-methoxyphenyl)-2-methanesulfonylethyl)-2,3-dihydro-1H-isoindole-1,3-dione, (Z)-(1-(3-ethoxy-4-methoxyphenyl)-2-(methylsulfanyl)ethylidene)(1-(naphthalen-2-yl)ethyl)amine, 1-(3-ethoxy-4-methoxyphenyl)-2-(methylsulfanyl)ethan-1-amine, and N-(2-((1S)-1-(3-ethoxy-4-methoxyphenyl)-2-(methylsulfanyl)ethyl)-1,3-dioxo-2,3-dihydro-1H-isoindol-4-yl)acetamide.    HA=resolving agent.