It has been shown earlier¹ that the relaxed force constants (RFCs) could be used as a measure of bond strength only when the bonds form a part of the complete valence internal coordinates (VIC) basis. However, if the bond is not a part of the complete VIC basis, its RFC is not necessarily a measure of bond strength. Sometimes, it is possible to have a complete VIC basis that does not contain the intramolecular hydrogen bond (IMHB) as part of the basis. This means the RFC of IMHB is not necessarily a measure of bond strength. However, we know that IMHB is a weak bond and hence its RFC has to be a measure of bond strength. We resolve this problem of IMHB not being part of the complete basis by postulating `equivalent’ basis sets where IMHB is part of the basis at least in one of the equivalent sets of VIC. As long as a given IMHB appears in one of the equivalent complete VIC basis sets, its RFC could be used as a measure of bond strength parameter.

A Biginelli reaction of β-ketonitriles, aldehydes and urea in principle can yield 5-cyano substituted dihydropyrimidinones. Although potentially very useful, this substituted heterocycle is often difficult to synthesize via the three component reaction, presumably due to the lack of stability of β-ketonitriles. The presentwork describes the development of reaction conditions yielding the desired product. Interesting mechanistic observations have also been noted. Thirteen new compounds (derivatives) of 5-cyanodihydropyrimidin were synthesized.

C-H activation in the synthesis of medicinally relevant molecules is reviewed. C-H activation is one of the most powerful components in the C-C or C-heteroatom bond formation tool box. This represents such an alternative which has provided the greener solutions to the organometallic/synthetic organic chemistry aimingto the synthesis of complex molecules. In recent years, there has been explosive growth in this area. In this review article we have presented effective methods of C-H activation employed in the synthesis of medicinally relevant molecules since 2010.