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(12) Patent Application Publication (10) Pub. No.: US 2015/0175532 A1 Mudduluru Et Al

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(12) Patent Application Publication (10) Pub. No.: US 2015/0175532 A1 Mudduluru Et Al US 2015O175532A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2015/0175532 A1 Mudduluru et al. (43) Pub. Date: Jun. 25, 2015 (54) PROCESS FOR PREPARATION OF (30) Foreign Application Priority Data 2,3-DIHYDROXY BENZONITRILE Jul. 19, 2012 (IN) ........................... 2926/CHFA2012 (71) Applicant: Laurus Labs Private Limited, Hyderabad (IN) Publication Classification (72) Inventors: Hari Krishna Mudduluru, Hyderabad (51) Int. Cl (IN); Shankar Madhavaram, we Hyderabad (IN) C07C 253/30 (2006.01) (52) U.S. Cl. (73) Assignee: Laurus Labs Private Limited, CPC .................................... C07C 253/30 (2013.01) Hyderabad (IN) (21) Appl. No.: 14/415,527 (57)57 ABSTRACT 1-1. The present invention relates to one pot process for the prepa (22) PCT Filed: Jul.18, 2013 ration of 2,3-dihydroxybenzonitrile from 2,3-dialkoxyben (86). PCT No.: PCT/N2O13AOOO447 Zoic acid without prior isolation of the intermediates. Further the invention relates to the preparation of 2,3-dihydroxyben S371 (c)(1), Zonitrile by dealkylation of 2,3-dialkoxybenzonitrile using (2) Date: Jan. 16, 2015 Suitable aluminum salt-amine complex. US 2015/0175532 A1 Jun. 25, 2015 PROCESS FOR PREPARATION OF 0006. Several reviews have been described for deprotec 2,3-DIHYDROXY BENZONITRILE tion of phenolic ethers. For example, phenolic methyl ethers have deprotected to remove the methyl moiety using hydro PRIORITY gen halide Such as hydrogen chloride or hydrogen bromide under highly acidic conditions; highly dark colored products 0001. This application claims the benefit under Indian Provisional Application No. 2926/CHF/2012 filed 19 Jul. formed in these reactions. In addition the phenolic com 2012 and entitled AN IMPROVED PROCESS FOR THE pounds react further with the halogen compounds used thus PREPARATION OF 2,3-DIHYDROXY BENZONITRILE”, setting a major drawback on this route. the content of which is incorporated by reference herein. 0007 Use of Lewis acids such as aluminum chloride or aluminum bromide in dealkylation is well known in the art. FIELD OF THE INVENTION U.S. Pat. No. 7.253,324 discloses a process of poly O-dealky lation of alkoxy aromatic compounds usinga aluminum chlo 0002 The present invention relates to one pot synthesis of ride-N,N-dimethylaniline complex. However the patent 2,3-dihydroxy benzonitrile from 2,3-dialkoxy benzoic acid restricts towards manufacture of polyphenols such as Res without isolating any intermediates. Veratrol, Oxyresveratrol and Gnetol. BACKGROUND OF THE INVENTION 0008. A conventional process for producing 2,3-dihy 0003. The substituted catechol compounds have a great droxy benzonitrile from 2,3-dimethoxy benzonitrile is dis commercial importance in the synthesis of pharmaceutical closed in Journal of Medicinal Chemistry, 2005, Vol. 48, No. compounds. 2,3-dihydroxybenzonitrile of Formula 1, a sub 3, 821-831. The disclosed process appears to be the closest stituted catechol compound is an important starting material prior art involving demethylation in the presence of boron for the preparation of a number of valuable heterocyclic com tribromide in dichloromethane. pounds which are medicinally important. 2,3-dihydroxyben 0009 Boron tribromide is highly moisture sensitive, col Zonitrile is the key starting material for Desferrithiocin and its orless fuming liquid and decomposes in air with evolution of analogues. Desferrithiocin (DFT) is an orally effective iron HBr. It is stored under a dry inert atmosphere and transferred chelator, with a similar high affinity and selectivity for iron to by syringe or through a Teflon tube for the reactions. It reacts desferrioxamine (DFO), which has been shown clinically to violently with protic solvents such as water and alcohols. possess antineoplastic activity. Therefore the commercial However the aforementioned process for preparing 2,3-dihy production for 2,3-dihydroxybenzonitrile is utmost impor droxybenzonitrile are less than fully satisfactory in view of tant. hazardous reagents, difficult to handle, expensive, lower tem peratures, long reaction times, tedious work up procedures, Formula I not liable for scale up process and low reaction yields, thereby OH limiting their use in commercial scale production. OH 0010 Despite all prior advances, available methods for synthesizing 2,3-dihydroxy benzonitrile from 2,3-dialkoxy benzoic acid which proceed through known intermediates CN Such as the corresponding acid 2,3-dialkoxy benzoyl chlo ride, 2,3-dialkoxy benzamide, 2,3-dialkoxy benzonitrile 0004 Several conventional processes for the preparation remain labor intensive, time consuming and environmentally of 2,3-dihydroxybenzonitrile are available in the literature. unfavorable. The isolated intermediates are however avail Various other procedures in the literature cites the preparation able in the literature, wherein the isolation of the intermedi of 2,3-dihydroxybenzonitrile from different starting materi ated are time consuming and practically not suitable for als (Substituted catechol compounds). A practically more manufacturing scales. Thus, there remains a need for a suitable process for the preparation of 2,3-dihydroxyben simple, cost effective, industrially feasible and scalable pro Zonitrile is from the corresponding precursor 2,3-dialkoxy cess for the synthesis of 2,3-dihydroxy benzonitrile that benzoic acid. A person skilled in the art expects the process to would avoid the aforementioned difficulties. proceed from acid halide, amide, nitrile and dealkylation, 0011. The present inventors thus found an alternate wherein the dealkylation step is mandatory to obtain the title approach for preparing 2,3-dihydroxybenzonitrile involving compound, Chemical and Pharmaceutical bulletin vol. 58, a one-pot synthesis from 2,3-dialkoxybenzoic acid without 11, 2010, 1552-1553 discloses the process for preparation of isolating any intermediates and also involving the use of 2,3-dihydroxy benzonitrile from 2,3-dihydroxy benzalde aluminum salt-amine complex for the dealkylation process. hyde in the presence of formic acid, hydroxylamine hydro chloride and sodium formate. 0005 European Journal of Organic Chemistry 11, 2006, SUMMARY OF THE INVENTION 2513-2516 discloses the process for preparation of 2,3-dihy droxy benzonitrile from 1,3-benzodioxole-4-carbaldehyde. 0012. The present invention encompasses a one pot pro Oxidative conversion of aldehydes to nitriles and deprotec cess for preparing 2,3-dihydroxybenzonitrile with high prod tion of hydroxy groups done in the presence of 2.2 eq of uct yield and quality. Sodium hexamethyldisilaZane in tetrahydrofuran and in 0013. In according with one embodiment, the present highly polar solvent 1,3-Dimethyl-2-imidazolidinone at 185° invention provides a one-pot process for the preparation of C. in a sealed tube. 2,3-dihydroxybenzonitrile of Formula I, US 2015/0175532 A1 Jun. 25, 2015 0021 b) quenching the resulting benzoic acid halide Formula I compound into a solution of aqueous ammonia to obtain OH corresponding amide of Formula III, OH 0022 c) treating the resulting solution of amide com pound with a suitable dehydrating reagent to obtain dialkoxybenzonitrile compound of Formula IV, and CN 0023 d) dealkylating the resulting solution of dialkoxy benzonitrile compound with aluminum salt-amine com plex to obtain 2,3-dihydroxybenzonitrile of Formula I. comprising the steps of 0024. In according with a third embodiment, the present 0014) a) reacting an acid compound of Formula (II) invention provides a process for preparation of 2,3-dihydroxy benzonitrile of Formula I, comprising: deprotecting dialkoxy benzonitrile compound of Formula IV; wherein R and Rare Formula II independently represents H or C. alkyl group, with a Suit OR able dealkylating agent in a Suitable organic solvent, wherein OR the dealkylating agent is aluminum salt-amine complex. Formula IV CO2H OR wherein R and R are independently represents H or Ca OR alkyl group with a suitable halogenating reagent in presence of a Suitable solvent to obtain corresponding benzoic acid halide, CN 0015 b) reacting the resulting benzoic acid halide com pound with a source of ammonia to obtain correspond 0025. In according with a fourth embodiment, the present ing amide of Formula III: invention provides a process for preparation of 2,3-dihydroxy benzonitrile of Formula I, comprising: deprotecting dialkoxy benzonitrile compound of Formula IV, wherein RandR are Formula III independently represents H or C. alkyl group, with alumi OR num salt-amine complex in a Suitable organic solvent; OR wherein the aluminium salt is selected from the group com prising aluminium chloride, aluminium bromide, aluminium iodide and the like and mixtures thereof, and amine is a CONH compound of formula NRaRbRc; in which: Ra, Rb and Rc independently represents a hydrogen, a linear 0016 c) treating the amide compound with a suitable or branched alkyl group, a linear or branched C-C alkenyl dehydrating reagent to obtain dialkoxy benzonitrile group, a C-C alkanol, a Cs-Co cycloalkyl group, a compound of Formula IV, and cycloalkylalkyl group, an aryl group, an aralkyl group or Ra, Rb or Ric may form a cyclic ring with nitrogen. Formula IV OR DETAILED DESCRIPTION OF THE INVENTION OR 0026. The present invention provides one pot process for the preparation of 2,3-dihydroxy benzonitrile from 2,3-di alkoxybenzoic acid suitable for the large scale preparation. CN 0027. In according with one embodiment, the present invention provides a one-pot process of 2,3-dihydroxyben 0017 d) dealkylating the resulting dialkoxy benzoni Zonitrile of Formula I, trile compound with a Suitable dealkylating agent; 0018 wherein the steps a) to d) are carried out in a Formula I single step without isolating any intermediates. OH 0019. In according with a second embodiment, the present OH invention provides a one-pot process for the preparation of 2,3-dihydroxybenzonitrile, comprising the steps of 0020 a) reacting an acid compound of Formula II, CN wherein R and Rare independently represents H or C alkyl group with a suitable halogenating reagent in pres ence of a suitable solvent to obtain corresponding ben comprising the steps of Zoic acid halide, 0028 a) reacting an acid compound of Formula (II) US 2015/0175532 A1 Jun.
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