28783-41-7

Basic information

• Product Name: 4,5,6,7-Tetrahydrothieno[3,2,c] pyridine hydrochloride
• Synonyms: 4,5,6.7-Tetrahydro-thienol[3,2-c]pyridine HCl;Thieno[3,2-c]pyridine, 4,5,6,7-tetrahydro-, hydrochloride;Clopidogrel Thieno IMpurity;TTP 4,5,6,7-Tetrahydrothieno 3,2-c Pyridine;4,5,6,7-Tetrahydrothieno[3,2-c]pyridine hydrochloride, 96%, 96%;4,5,6,7-tetrahydrothineo [3,2-c]pyridine hydrochloride;4,5,6,7-TETRAHYDROTHIENO[3,2,C] PYRIDINE HCL;4,5,6,7-TETRAHYDROTHIENO[3,2-C]PYRIDINE HYDROCHLORIDE
• CAS NO: 28783-41-7
• Molecular Formula: C₇H₉NS*ClH
• Molecular Weight: 139.22
• EINECS: 249-220-0
• Product Categories: Heterocycle-Pyridine series;Prasugrel Intermediates;Heterocyclic Compounds;Bases & Related Reagents;Heterocycles;Nucleotides;Sulfur & Selenium Compounds;Intermediates
• Mol File: 28783-41-7.mol
• Article Data: 12

Chemical Properties

• Melting Point: 212-215°C
• Boiling Point: 242.9 °C at 760 mmHg
• Flash Point: 100.7 °C
• Appearance: /
• Density: 1.143g/cm3
• Vapor Pressure: 0.0331mmHg at 25°C
• Storage Temp.: Keep in dark place,Inert atmosphere,Room temperature
• Solubility: DMSO, Methanol, Water
• CAS DataBase Reference: 4,5,6,7-Tetrahydrothieno[3,2,c] pyridine hydrochloride(CAS DataBase Reference)
• NIST Chemistry Reference: 4,5,6,7-Tetrahydrothieno[3,2,c] pyridine hydrochloride(28783-41-7)
• EPA Substance Registry System: 4,5,6,7-Tetrahydrothieno[3,2,c] pyridine hydrochloride(28783-41-7)

Safety Data

• Statements: 36/37/38
• Safety Statements: 26-36/37/39-37
• RIDADR: UN2811
• HazardClass: IRRITANT
• Hazardous Substances Data: 28783-41-7(Hazardous Substances Data)

Usage

Chemical Properties

Off-White Solid

Uses

An intemediate of Clopidogrel and Prasugrel.

InChI:InChI=1/C7H9NS.ClH/c1-3-8-5-6-2-4-9-7(1)6;/h2,4,8H,1,3,5H2;1H

Synthetic route

[2-(2-thyenyl)ethyl]amine (30433-91-1) + formaldehyd (50-00-0) → 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7)

Conditions	Yield
Stage #1: [2-(2-thyenyl)ethyl]amine; formaldehyd In dichloromethane at 40 - 45℃; Stage #2: With hydrogenchloride In dichloromethane; water; N,N-dimethyl-formamide at 20 - 70℃;	99%
Stage #1: [2-(2-thyenyl)ethyl]amine; formaldehyd In toluene for 1.5h; Reflux; Inert atmosphere; Dean-Stark; Stage #2: With hydrogenchloride In 1,4-dioxane; toluene at 60℃; for 0.5h; Inert atmosphere;	98%
Stage #1: [2-(2-thyenyl)ethyl]amine; formaldehyd In 1,2-dichloro-ethane for 4h; Heating / reflux; Stage #2: With hydrogenchloride In 1,2-dichloro-ethane; N,N-dimethyl-formamide at 70℃; for 4h;	90%

N-methoxycarbonyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine (68559-49-9) → 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7)

Conditions	Yield
Stage #1: N-methoxycarbonyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine With sodium hydroxide In methanol for 12h; Reflux; Stage #2: With hydrogenchloride In 1,4-dioxane pH=1;	82%

N-methylene-2-(thien-2-yl)ethanamine (111954-31-5) → 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7)

Conditions	Yield
With hydrogenchloride In N,N-dimethyl-formamide
With hydrogenchloride In isopropyl alcohol at 60℃; for 5h;

dihydro-6,7 thieno<3,2-c>pyridine (107112-93-6) → 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7)

Conditions	Yield
Stage #1: dihydro-6,7 thieno<3,2-c>pyridine With methanol; sodium tetrahydroborate at 20℃; for 2h; Stage #2: With hydrogenchloride

2-thiophenethanol (5402-55-1) → 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7)

Conditions	Yield
Multi-step reaction with 4 steps 1: triethylamine / dichloromethane / 2 h / -5 - 20 °C 2: formic acid / 8.5 h / 80 °C / Inert atmosphere 3: trifluoroacetic acid / 20 °C 4: sodium tetrahydroborate; methanol / 2 h / 20 °C View Scheme

2-(2-thienyl)ethyl tosylate (40412-06-4) → 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7)

Conditions	Yield
Multi-step reaction with 3 steps 1: formic acid / 8.5 h / 80 °C / Inert atmosphere 2: trifluoroacetic acid / 20 °C 3: sodium tetrahydroborate; methanol / 2 h / 20 °C View Scheme

di-tert-butyl dicarbonate (24424-99-5) + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → 6,7-dihydro-4H-thieno[3,2-c]-pyridine-5-carboxylic acid tert-butyl ester (230301-73-2)

Conditions	Yield
With triethylamine In dichloromethane at 20℃; for 2h;	100%
With triethylamine In dichloromethane at 20℃; for 4.5h;	100%
With triethylamine In dichloromethane at 20℃; for 6h;	92.3%
Stage #1: 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With potassium carbonate In 1,4-dioxane at 80℃; for 0.5h; Stage #2: di-tert-butyl dicarbonate In 1,4-dioxane for 1h;	16.8 g

trityl chloride (76-83-5) + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → 5-trityl-4,5,6,7-tetrahydro-tieno[3,2-c]pyridine (109904-25-8)

Conditions	Yield
With triethylamine In dichloromethane at 20℃; for 2h; Inert atmosphere;	100%
With triethylamine In dichloromethane at 12 - 28℃;	99%
With N-ethyl-N,N-diisopropylamine In acetonitrile for 3h;	94%

C15H13ClO5S + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → (S)-(+)-clopidogrel (113665-84-2)

Conditions	Yield
With sodium carbonate In dichloromethane at 25 - 40℃; for 24h; Temperature;	97.02%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) + benzyl chloride (100-44-7) → 5-benzyl-4,5,6,7-tetrahydro-thieno[3,2-c]-pyridine (55142-78-4)

Conditions	Yield
With tetra(n-butyl)ammonium hydrogensulfate; potassium carbonate In acetonitrile at 70℃;	97%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → 4,5,6,7-tetrahydrothieno[3,2-c]pyridine (54903-50-3)

Conditions	Yield
With water; potassium hydroxide In toluene at 25 - 30℃;	96.5%
With sodium hydroxide In dichloromethane at 20℃; for 3.5h;	3.12 g

methyl (R)-2-(2-chlorophenyl)-2-benzenesulfonyloxyacetate (223123-46-4) + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → (S)-(+)-clopidogrel bisulfate (120202-66-6)

Conditions	Yield
Stage #1: methyl (R)-2-(2-chlorophenyl)-2-benzenesulfonyloxyacetate; 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With sodium hydrogencarbonate In acetone for 6h; Reflux; Stage #2: With sulfuric acid In acetone	95.2%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) + N,N-dimethyl-formamide (68-12-2, 33513-42-7) → 4,5,6,7-tetrahydrothieno[3,2-c]pyridine-5-carbaldehyde (29079-79-6)

Conditions	Yield
With molybdenum (IV) sulfide at 150℃; for 18h;	95%
at 150℃; for 96h; Inert atmosphere; Sealed tube;	89%
With graphene oxide at 150℃; for 18h; Sealed tube;	81%

(R)-2-(2-chlorophenyl)-2-(4-nitrobenzenesulfonyloxy)acetic acid methyl ester + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → (S)-(+)-clopidogrel bisulfate (120202-66-6)

Conditions	Yield
Stage #1: (R)-2-(2-chlorophenyl)-2-(4-nitrobenzenesulfonyloxy)acetic acid methyl ester; 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With potassium carbonate In acetone at 20℃; for 24h; Stage #2: With sulfuric acid In acetone	93.1%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) + N,N-dimethyl-formamide (68-12-2, 33513-42-7) → C8H9NOS*ClH

Conditions	Yield
With manganese(II) chloride tetrahydrate at 150℃; for 10h; Inert atmosphere; Sealed tube;	93%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) + 1-(((2R,3R)-2-(2,4-difluorophenyl)-3-methyloxiran-2-yl)-methyl)-1H-1,2,4-triazole (135270-13-2) → C19H20F2N4OS

Conditions	Yield
With magnesium 2-methylpropan-2-olate In acetonitrile for 16h; Inert atmosphere; Reflux;	93%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) + cyclopropanecarboxylic acid chloride (4023-34-1) → cyclopropyl(6,7-dihydrothieno[3,2-c]pyridin-5(4H)-yl)methanone

Conditions	Yield
With triethylamine In tetrahydrofuran at 0℃; for 1h;	93%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) + methyl 2-bromo-2-(2-chlorophenyl)acetate (85259-19-4) → clopidogrel bisulfate (135046-48-9)

Conditions	Yield
Stage #1: 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With sodium carbonate In water at 25℃; for 0.5h; Stage #2: methyl 2-bromo-2-(2-chlorophenyl)acetate In water; toluene at 20℃; for 12h; Stage #3: With sulfuric acid In ethyl acetate for 1h; Reagent/catalyst; Solvent;	90%
Stage #1: 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride; methyl 2-bromo-2-(2-chlorophenyl)acetate With potassium carbonate In acetone Stage #2: With sulfuric acid

di-tert-butyl dicarbonate (24424-99-5) + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → 2-bromo-6,7-dihydrothieno[3,2-c]pyridine-5(4H)-carboxylic acid tert-butyl ester (949922-62-7)

Conditions	Yield
Stage #1: di-tert-butyl dicarbonate; 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With tert-butyl methyl ether; sodium hydroxide In water at 0℃; Stage #2: With bromine In water at 0 - 20℃; for 1.5h;	88.32%

α-bromo-2-chlorophenyl acetic acid (29270-30-2) + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → 2-(2-chlorophenyl)-2-(6,7-dihydrothieno[3,2-c]pyridine-5(4H)-yl)acetic acid (90055-55-3)

Conditions	Yield
Stage #1: α-bromo-2-chlorophenyl acetic acid; 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With potassium hydroxide In methanol; water at 10 - 40℃; for 3h; Stage #2: With hydrogenchloride In methanol; water at 5 - 20℃; for 4h; pH=3.5;	88%
Stage #1: α-bromo-2-chlorophenyl acetic acid; 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With potassium hydroxide In methanol; water at 15 - 40℃; for 3h; Stage #2: With hydrogenchloride In methanol; water at 20℃; for 2h; pH=3.5;	88%
Stage #1: 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With sodium hydroxide In water at 20 - 35℃; Stage #2: α-bromo-2-chlorophenyl acetic acid In water at 20 - 27℃; Stage #3: With hydrogenchloride In water; ethyl acetate at 20 - 30℃; pH=3.5 - 4.5;
With potassium hydroxide In water at 0 - 20℃; for 24h;	12 g

sodium cyanide (143-33-9) + 2-chloro-benzaldehyde (89-98-5) + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → 2-(2-chlorophenyl)-2-(6,7-dihydrothieno[3,2-c]pyridine-5(4H)-yl)acetonitrile (444728-11-4)

Conditions	Yield
Stage #1: sodium cyanide; 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride In methanol; water for 0.666667h; Stage #2: 2-chloro-benzaldehyde In methanol; water at 23 - 50℃; for 6h; Stage #3: With sodium metabisulfite In methanol; water at 25 - 30℃; for 2h;	87.4%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) + (+/-)α-chloro-2-(2-chlorophenyl)acetonitrile (5829-89-0) → 2-(2-chlorophenyl)-2-(6,7-dihydrothieno[3,2-c]pyridine-5(4H)-yl)acetonitrile (444728-11-4)

Conditions	Yield
With sodium hydrogencarbonate In butan-1-ol for 3h; Product distribution / selectivity; Heating / reflux;	86%

2-bromo-2-(2-chlorophenyl)acetonitrile (444891-19-4) + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → 2-(2-chlorophenyl)-2-(6,7-dihydrothieno[3,2-c]pyridine-5(4H)-yl)acetonitrile (444728-11-4)

Conditions	Yield
With sodium hydrogencarbonate In methanol for 3h; Product distribution / selectivity; Heating / reflux;	85%
With sodium hydrogencarbonate In methanol for 3h; Heating / reflux;	85%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) + p-acetylaminobenzenesulfonyl chloride (121-60-8) → N-(4-{6,7-dihydrothieno[3,2-c]pyridin-5(4H)-ylsulfonyl}phenyl)acetamide (949779-15-1)

Conditions	Yield
With triethylamine In acetonitrile for 5h; Reflux;	84.5%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → thieno[3,2-c]pyridine (272-14-0)

Conditions	Yield
Stage #1: 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With water; sodium hydroxide In dichloromethane at 20℃; Stage #2: With manganese(IV) oxide In toluene at 140℃; for 24h;	84.42%
Stage #1: 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With sodium hydroxide In water for 2h; Stage #2: With manganese(IV) oxide In toluene at 130℃;	650 mg

1-isocyanocyclohexene (1121-57-9) + 2-chloro-benzaldehyde (89-98-5) + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → 2-(2-chlorophenyl)-N-cyclohex-2-enyl-2-(6,7-dihydro-4H-thieno[3,2-c]pyridin-5-yl)acetamide (1130832-62-0)

Conditions	Yield
Stage #1: 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With triethylamine In methanol at 20℃; for 0.0833333h; Stage #2: 2-chloro-benzaldehyde In methanol at 20℃; for 1h; Ugi reaction; Stage #3: 1-isocyanocyclohexene With formic acid In methanol at 60℃; for 1h; Ugi reaction; Microwave irradiation;	83%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) + Cinnamyl bromide (4392-24-9) → 5-cinnamyl-4,5,6,7-tetrahydrothieno[3,2-c]pyridine (1581720-50-4)

Conditions	Yield
Stage #1: 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With sodium hydroxide In water at 0 - 25℃; for 0.166667h; Inert atmosphere; Stage #2: Cinnamyl bromide With triethylamine In tetrahydrofuran; water for 0.333333h; Inert atmosphere;	76%

formaldehyd (50-00-0) + tanshinone IIA (568-72-9) + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → C27H27NO3S

Conditions	Yield
With copper diacetate; acetic acid In dimethyl sulfoxide at 60℃;	76%

(R)-2-(2-chlorophenyl)-2-(4-nitro sulfonyloxy)acetic acid methyl ester-d3 + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → (S)-2-(2-chlorophenyl)-2-(6,7-dihydrothieno[3,2-c]pyridine-5(4H)-yl)acetic acid methyl ester-d3 (1093351-48-4)

Conditions	Yield
With potassium hydrogencarbonate In acetonitrile at 20℃; for 24h; Inert atmosphere;	73.6%

5-bromo-2,3-dihydro-2,2-dimethyl-7-(4-bromo-butoxy)-benzofuran (1089210-23-0) + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → 1-[(5-bromo-2,3-dihydro-2,2-dimethyl-benzofuran-7-yl)-oxy]-4-(4,5,6,7-tetrahydro-thieno[3,2-c]pyridin-5-yl)-butane (1089209-66-4)

Conditions	Yield
With sodium hydroxide; triethylbutylammonium chloride In chloroform; water at 20 - 60℃; for 28h;	73.3%

2-bromo-1-cyclopropyl-2-(2-fluorophenyl)ethanone (204205-33-4) + 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) → 1-cyclopropyl-2-(6,7-dihydrothieno[3,2-c]pyridin-5(4H)-yl)-2-(2-fluorophenyl)ethanone hydrobromide salt (1287752-37-7)

Conditions	Yield
Stage #1: 6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride With potassium hydrogencarbonate at 20℃; for 0.5h; Stage #2: 2-bromo-1-cyclopropyl-2-(2-fluorophenyl)ethanone In acetonitrile at 20℃; for 25h; Stage #3: With hydrogen bromide In water; acetone at 10 - 20℃; for 3h; Reagent/catalyst;	73.1%
Multi-step reaction with 2 steps 1: potassium carbonate / acetonitrile / 5 h / 25 - 35 °C 2: hydrogen bromide / water; acetone / 5.25 h / 0 - 30 °C View Scheme

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) + 4'-(bromomethyl)-1,1'-biphenyl-2-carbonitrile (114772-54-2) → 4'-(6,7-dihydro-4H-thieno[3,2-c]pyridin-5-ylmethyl)biphenyl-2-carbonitrile (938904-49-5)

Conditions	Yield
With potassium carbonate In methanol	72%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) + propargyl bromide (106-96-7) → 5-(prop-2-yn-1-yl)-4,5,6,7-tetrahydrothieno[3,2-c]pyridine

Conditions	Yield
With potassium carbonate In N,N-dimethyl-formamide at 20℃; for 16h;	72%
With potassium carbonate In N,N-dimethyl-formamide at 20℃; for 16h;	72%

6,7-dihydro-4H-thieno[3,2-c]pyridine hydrochloride (28783-41-7) + tert-butyl 4-(2-iodoethyl)piperidine-1-carboxylate (89151-46-2) → 5-<2-(N-Boc-4-piperidinyl)ethyl>-4,5,6,7-tetrahydrothieno<3,2-c>pyridine (158149-68-9)

Conditions	Yield
With sodium hydroxide; Aliquat 336 In dichloromethane for 20h;	70%
With sodium hydroxide In dichloromethane

Upstream product

• 30433-91-1 [2-(2-thyenyl)ethyl]amine 
• 50-00-0 formaldehyd 
• 111954-31-5 N-(thiophen-2-ylethyl)methyleneamine 
• 40412-06-4 2-(2-thienyl)ethyl tosylate 
• 5402-55-1 2-thiophenethanol 
• 107112-93-6 dihydro-6,7 thieno<3,2-c>pyridine 
• 68559-49-9 N-methoxycarbonyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine 

Downstream Products

• 135046-48-9 clopidogrel bisulfate 
• 90055-48-4 clopidogrel 
• 165947-48-8 5-tert-butoxycarbonyl-4,5,6,7-tetrahydrothieno[3,2-c]pyridine-2-carboxylic acid 
• 949922-62-7 2-bromo-6,7-dihydrothieno[3,2-c]pyridine-5(4H)-carboxylic acid tert-butyl ester 
• 1620757-13-2 5-((5-benzyl-1H-1,2,4-triazol-3-yl)methyl)-4,5,6,7-tetrahydrothieno[3,2-c]pyridine 
• 1620757-12-1 5-((5-(4-methoxybenzyl)-1H-1,2,4-triazol-3-yl)methyl)-4,5,6,7-tetrahydrothieno[3,2-c]pyridine 
• 1620757-11-0 5-((5-(4-fluorobenzyl)-1H-1,2,4-triazol-3-yl)methyl)-4,5,6,7-tetrahydrothieno[3,2-c]pyridine 
• 1620757-10-9 2-((3-((6,7-dihydrothieno[3,2-c]pyridin-5(4H)-yl)methyl)-1H-1,2,4-triazol-5-yl)methyl)aniline 
• 1620757-09-6 5-((5-phenyl-1H-1,2,4-triazol-3-yl)methyl)-4,5,6,7-tetrahydrothieno[3,2-c]pyridine 
• 1620757-08-5 5-((5-(3-chlorophenyl)-1H-1,2,4-triazol-3-yl)methyl)-4,5,6,7-tetrahydrothieno[3,2-c]pyridine 
• 1620757-07-4 5-((5-phenyl-1H-1,2,4-triazol-3-yl)methyl)-4,5,6,7-tetrahydrothieno[3,2-c]pyridine 
• 1620757-06-3 5-((5-(4-chlorophenyl)-1H-1,2,4-triazol-3-yl)methyl)-4,5,6,7-tetrahydrothieno[3,2-c]pyridine 

Relevant articles and documents

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AN IMPROVED PROCESS FOR THE PREPARATION OF PRASUGREL HYDROCHLORIDE AND ITS INTERMEDIATES

The present invention provides an improved process for the preparation of prasugrel and its pharmaceutical acceptable salt. Prasugrel chemically known as 2-acetoxy-5-(a- cyclopropylcarbonyl-2-fluorobenzyl)-4,5,6,7-tetrahydrothieno[3,2-c]-pyridine or 5-[2- cyclopropyl-l-(2-fluorophenyl)-2-oxoethyl]-4,5,6,7-tetrahydrothieno[3,2,-c]pyridine- 2yl acetate and having the structural formula (I) and its pharmaceutically acceptable salts. The present invention also provides an improved process for the preparation of cyclopropyl 2-fluorobenzyl ketone, 2-Fluoro-a-cyclopropyl carbonylbenzyl bromide, 5,6,7,7a Tetrahydro-4H- theino-[3,2-c]- pyridone-2 p-toluenesulfonate and its hydrochloride salt.