Novel 1,3,4-thiadiazole(s) useful as liq. crystal intermediates

摘要

Novel 1,3,4-thiadiazoles of formula (I) are claimed, as are also (i) the use of (I) as intermediates in the prodn. of components for liq. crystal mixts.; and (ii) the prepn. of the 2-halo derivs. of formula (I) by (a) reacting 2-amino-1,3,4-thiadiazole with Br2; (b) diazotising the 2-bromo cpd. thus obtd.; (c) reacting the diazonium salt with Br2; and (d) reacting the 2,5-dibromo-1,3,4thiadiazole with a boron cpd. of formula (II) under transition metal catalysis in an inert solvent at -78 to 200 deg.C. X-B-A<1>-(M<1>-A<2>-)m(M<2>-A<3>)n-R<1> (I); Q<1>Q<2>-B-A<1>-(M<1>-A<2>)m(-M<2>-A<3>)n-R<1> (II) (sic) and (IIA); X=Cl, Br or I; B=1,3,4-thiadiazol-2,5-diyl; A<1>-A<3>=1,4-phenylene, pyridin-2,5-diyl, naphthalene-2,6-diyl or bicyclo2.2.2 octan-1,4-diyl (with 1 or more H in each of these opt. replaced by F, Cl and/or CN); pyrazin-2,5-diyl, pyridazin-3,6- diyl, pyrimidin-2,5 diyl or thiophen-2,4-diyl (with 1 or 2H in each of these opt. replaced by F, Cl and/or CN); trans-1,4-cyclohexylene (with 1 or 2H opt. replaced by CN and/or Me); 1,3-thiazol-2,4- or 2,5-diyl or thiophen- 2,4-diyl (with 1H of each of these opt. replaced by F, Cl and/or CN); or (1,3,4)-thiadiazol-2,5-diyl, 1,3-dioxan-2,5-diyl 1,3-dithian-2,5-diyl, piperazin-1,4- or 2,5-diyl or 1,3-dioxaborinan-2,5-diyl; M<1> and M<2>=-CO.O-, -O.CO-, -O.CO.O-, -O.CS.O-, -CH2O, -OCH2-, -CH=CH-, -C?=C- or a single bond; R<1>=O-benzyl, H or 1-12C alkyl or alkoxy; m and n=0 or 1; and Q<1> and Q<2>=-OH, 1-4C alkoxy, 1-4C alkyl, Ph (opt. substd. by halogen, 1-4C alkoxy or 1-4C alkyl) or halogen or Q<1> and Q<2> together form a 1-4C alkylenedioxy gp., a methylene gp. (opt. substd. by one or two 1-4C alkyl) or Q<1>, Q<2> and the boron atom are part of a boroxine ring of formula (IIA). NB. In the disclosure (II) is an organometallic cpd. with Y replacing Q<1>Q<2> and being halogen-Mg, Li or -BQ<1>Q<2>.