NOVELTY - Making Buprenorphine involves contacting thebaine with methyl vinyl ketone; reducing 7 alpha -acetyl-6,14-endo-etheno-6,7,8,14-tetrahydrothebaine by catalytic hydrogenation; contacting 7 alpha -acetyl-6,14-endo-ethano-6,7,8,14-tetrahydrothebaine with tertiary butyl metal halide followed by contacting with cynogen bromide, alkali metal hydroxide, and cyclopropyl methyl-halide in solvent; and contacting formed N-cyclopropylmethyl-7 alpha -(2-hydroxy-3,3-dimethyl-2-butyl)-6,14-endo-ethano-6,7,8,14-tetrahydronorthebaine with alkanethiol and base in solvent to give the compound (I).    USE - For the preparation of Buprenorphine (claimed) which is used in the treatment of moderate to severe pain and opioid dependence.    ADVANTAGE - The method is an efficient and industrially scalable process; produces Buprenorphine in high purity with enhanced safety and eco-friendly norms; produces Buprenorphine with overall yield of 40-42%, which is higher than the prior art yield of 26-28% disclosed in US 2011/0152527A1; avoids the use of hazardous, lacrymatic, toxic and expensive raw material; provides simpler work-up procedure; and reduces the number of solvents in the process of preparation buprenorphine and the intermediates of it to render the process economically viable.    DETAILED DESCRIPTION - Preparation (P1) of Buprenorphine (I), involves (a) contacting (5 alpha )-6,7,8,14-tetrahydro-4,5-epoxy-3,6-dimethoxy-17-methylrnorphinan i.e. thebaine (II) with methyl vinyl ketone (MVK) in a solvent to obtain 7 alpha -acetyl-6,14-endo-etheno-6,7,8,14-tetrahydrothebaine (III); (b) reducing the compound (III) of step (a) by catalytic hydrogenation or by catalytic transfer hydrogen reaction in a solvent to obtain 7 alpha -acetyl-6,14-endo-ethano-6,7,8,14-tetrahydrothebaine (IV); (c) contacting the compound (IV) of step (b) with tertiary butyl metal halide in a solvent to obtain 7 alpha -(2-hydroxy-3,3-dimethyl-2-butyl)-6,14-endo-ethano-6,7,8,14-tetrahydrothebaine (V); (d) contacting compound (V) of step (c) with cynogen bromide in a solvent to yield N-cyano-7 alpha -(2-hydroxy-3,3-dimethyl-2-butyl)-6,14-endo-ethano-6,7,8,14-tetrahydronorthebaine (VI); (e) contacting the compound (VI) with alkali metal hydroxide in a solvent to obtain 7 alpha -(2-hydroxy-3,3-dimethyl-2-butyl)-6,14-endo-ethano-6,7,8,14-tetrahydronorthebaine (VII); (f) contacting the compound (VII) obtained in step (e) with cyclopropyl methyl-L' in a solvent to produce N-cyclopropylmethyl-7 alpha -(2-hydroxy-3,3-dimethyl-2-butyl)-6,14-endo-ethano-6,7,8,14-tetrahydronorthebaine (IX); and g) contacting the compound (IX) obtained in step (f) with alkanethiol and base in a solvent to produce the compound (I).    L'=leaving group selected from halides, tosyl, or mesyl.    INDEPENDENT CLAIMS are included for the following:    (1) preparing (V) involving contacting the compound (IV) with tertiary butyl metal halide in cyclopentyl methyl ether (CPME);    (2) an in-situ process for the preparation of compound (VI), involving contacting the compound (IV) with tertiary butyl metal halide in CPME to obtain the compound (V) followed by reaction with cyanogen bromide to obtain the compound (VI) without isolating the compound (V);    (3) preparing the compound (IX) involving contacting the compound (VII) with cyclopropyl methyl halide in the presence of acid excavenger in solvent selected from acetonitrile (ACN) or CPME to obtain compound (IX).