We present a convenient synthesis of novel heteroaryl-fused 3-oxo-1,4-thiazepine-5-carboxamides and 5-oxo-1,4-thiazepine-3-carboxamides using a modification of four-component Ugi condensation. We demonstrate the usefulness and versatility of the developed approach for the synthesis of variously substituted compounds and discuss the scope and limitations of the chemistry involved.

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Dielectric spectroscopy of a ferroelectric liquid crystal with planar texture in the frequency range 100 Hz to 1 MHz has been carried out as a function of temperature from 25°C to 60°C at different DC fields varying from 0 to 12 kVcm-'. From the measured dielectric strengths and relaxation frequencies, it is observed that the material has a SY-SX transition at 56.1"C and a SX-I transition at 58°C. The data of the SE phase have been assigned to the Goldstone mode. The rotational viscosity and elastic constant have been calculated from the observed data. The capacitance shows an abrupt drop at the critical DC field where unwinding of the helix occurs. The measured value of the critical field decreases with temperature and agrees to literature data from electrooptical experiments. On applying a DC field greater than 6.5 kVcm-' at room temperature, the liquid crystal shows the unwound S z and S; phases. IntroductionThe complex dielectric permittivity of a ferroelectric liquid crystal can be directly measured by dielectric spectroscopic techniques. With the emergence of enhanced accuracies of computer controlled bridges, it is possible to acquire dielectric permittivity and dielectric loss data rather quickly over a wide frequency range at very small frequency steps. The dielectric spectroscopy of a large number of ferroelectric liquid crystals have been recently reported and possible information about the molecular orientation and the relaxation processes have been discussed [ 1-10]. The planar oriented ferroelectric liquid crystal exhibits the chiral smectic C S,* phase over a wide temperature range; the dielectric behaviour of this phase is described to two relaxation processes [l, 91. The dominant Goldstone mode appears because of the fluctuations of the phase in the azimuthal orientation of the director, whereas the soft mode appears due to the fluctuations in the amplitude of the tilt angle 0. The dielectric relaxation frequencies of the Goldstone mode are weakly dependent on the tempera-