TECHNOLOGY FOCUS - ELECTRONICS - Preferred Transistor: The organic thin-film transistor has an organic semiconductor layer, gate electrode placed on the organic semiconductor layer, with a gate insulating layer interposed between them, a source electrode and a drain electrode which are arranged opposite to each other, with the organic semiconductor layer interposed between them.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Disclosed): Preparation of (I) involves brominating substituted cyclopentanone compound using NBS, NH4OAc in Et2O to form corresponding 2 or 5-bromo derivative; reacting the 2 or 5-bromo derivative with KSCSO-i-Pr in acetone to form corresponding thio ester derivative; and reacting the thio ester derivative with H2SO4 followed by P(OEt)3 to form (I). Preferred Definitions:    R1 and R2=3-10C branched alkyl.    SPECIFIC COMPOUNDS - 4 Compounds i.e. beta -Me-hexamethylenetetrathiafulvalene (HMTTF) of formula (I'), beta -t-Bu-HMTTF, beta -n-pentyl-HMTTF and beta -tert-pentyl-HMTTF are disclosed as the hexamethylenetetrathiafulvalene compound (I).    EXAMPLE - In 10 ml of diethyl ether were dissolved 5.0 g or 51 mmol of 3-methylcyclopentanone (2a), 9.3 g or 52 mmol of N-bromosuccinimide (NBS), and 0.39 g or 5.0 mmol of ammonium acetate, followed by stirring for five hours. The resulting light yellowish solution was filtered off, and the filtrate was given diethyl ether and water. After separation into two layers, the diethyl ether layer was freed of diethyl ether by using an evaporator. Thus there was obtained a yellowish oily compound (2b). The compound (2b) was dissolved in 40 ml of acetone and the resulting solution was added little by little to 8.7 g or 50 mmol of potassium isopropyl xanthate, followed by stirring for an hour. The resulting yellowish brown suspension was filtered off, and the filtrate was freed of acetone by using an evaporator. Thus there was obtained a yellowish brown oily compound (2c). The compound (2c) was slowly added dropwise to 10 ml of ice-cooled concentrated sulfuric acid. After stirring for an hour, the solution was dropped onto about 40 g of ice. There was obtained a milky white suspension. From this suspension was extracted with dichloromethane the desired organic matter, which was subsequently washed with distilled water, dried with magnesium sulfate, and freed of dichloromethane by using an evaporator. Thus there was obtained a light yellowish oily compound (2d). The compound (2d) was given 3 ml of triethyl phosphite, followed by reaction at 130 degrees C for 12 hours under nitrogen. The resulting reaction liquid was given methanol to yield yellowish solids, which were filtered out and recrystallized four times from ethanol. Thus there was obtained 0.081 g or 0.26 mmol of beta -Me-hexamethylenetetrathiafulvalene (HMTTF) (yield 1.1% and m.p. 130 degrees C) in the form of yellowish needle crystal. An organic semiconductor thin film (test) comprising the compound beta -Me-HMTTF was prepared. A control organic semiconductor thin film comprising 5,6,5',6'-tetrahydro-4H,4'H-(2,2')bi(cyclopenta(1,3)dithiolylidene) was prepared in a similar manner as the test. The test/control transistors were evaluated for mobility, threshold voltage and on-off ratio. The results for test/control were: mobility ( mu ) (cm2/Vs) = 2.6x 10-3/3.6, threshold voltage (V) = 7.6/27 and on-off ratio = 1x 103/3x 103.