Cyanogen chloride reactivity

The 1,3,5-triazines are all synthesized by nucleophilic substitution of cyanuric chloride, which in turn is made by trimerization of cyanogen chloride. As each chlorine is replaced, the reactivity of the remaining ones diminishes. Thus the first displacement takes place at room temperature or below, the second requires moderate heat and the third needs strong heating (Scheme 1). The chemistry of the triazine herbicides has been reviewed (B-75MI10700, B-60MI10700). 

Chlorosulfonyl isocyanate6 (CSI) (57) is a very reactive compound which was first prepared from cyanogen chloride (56) and sulfur trioxide (Graf, 1956) (Scheme 31). CSI (57) undergoes [2+2] cycloaddition reactions with various alkenes initial adducts like (58) and (59) may be hydrolysed to the b-lactams (60) and (61). The cycloaddition reaction also occurs with enamines (62) to give products like (63) and (64) (Scheme 32). 

Cyanuric chloride (2,4,6-trichloro-l,3,5-triazine), mp 145" C, bp 190°C, is produced commercially by gaseous trimerization of cyanogen chloride over charcoal catalysts. Cyanuric chloride behaves as a heterocyclic acid chloride analogue. Its reactive chlorine atoms are easily substituted (also stepwise) by S]sjAr processes ... 

Cyanogen chloride becomes volatile as temperatures increase, and the DOT lists it as a 2.3 poison gas. The NEPA 704 designation for CK is estimated to be health 4, flammability 0, reactivity 2, and special -0. Cyanogen chloride vapors are highly toxic. It has a 4-digit UN identification number of 1589 (inhibited). Treatment for either AC or CK poisoning is to follow the treatment protocols for Airway, Breathing,... 

The positional reactivity of dibenzofuran in electrophilic substitution reactions depends on the electrophile. Reaction occurs mostly at the 2- and 3-positions but the ratio of the two products varies (91JOC4671). The reaction of cyanogen bromide catalyzed by aluminum chloride gives an 80% yield of the 2-substituted product together with 15% of the 3-cyano-derivative (92ACS312). Oxidative acetoxylation of dibenzofuran occurs predominantly at the 3-position ( 60%) together with attack at the 1-position ( 30%) (92ACS802). In this latter reaction, the attack by acetate is on the dibenzofuranium radical cation. 

Two syntheses of this alkaloid (119) have been reported. In one of them (120), starting from conessine (XCVI), the more reactive 3/3-nitrogen was protected by a selective reaction with 1 mole of hydrogen peroxide to form the 3-mono-IV-oxide CXX subsequent treatment with cyanogen bromide yielded iV-cyanoconessimine-3-IV -oxide (CXXI) which on reduction of the A -oxide grouping with sodium borohydride and aluminum chloride followed by alkaline hydrolysis yielded conessimine. 

---