Hydrogen bromide cyanate

Recently Allenstein and Quis ( ) investigated the addition of hydrogen halides to thiocyanates. While with hydrogen chloride only labile adducts have been observed, hydrogen bromide adds to methyl- and phenylthio-cyanate to afford 2 1 adducts, for which structure XX has been assigned on the basis of infrared spectroscopy ( ). 

The reaction of aryl cyanates with hydrogen chloride or hydrogen bromide in an inert solvent produces the haloformimidinium halides XL ( ). 

In addition, stereoselective synthesis of solenopsin A has been reported by four research groups. An approach utilizing the stereoselective reductive de-cyanation (596) starts with aminonitrile 229, prepared from 2-picoline. It was selectively hydrogenated in the presence of Pd-C, followed by alkylation with undecyl bromide, affording 231. Reductive decyanation of 231 with NaBH4 in MeOH led to predominant (8 2) formation of the trans isomer (232) which was then debenzylated to ( )-solenopsin A (Id). The cis product (Ic) was in turn prepared by treatment of 231 with sodium in liquid ammonia followed by de-benzylation (Scheme 10). 

---