Lewis acids sodium cyanide

Selenocyanates produce selenols or diselenides upon either reduction (e g. with sodium borohydride) or hydrolysis (see Scheme 1). They undergo displacement of the cyanide ion by various nucleophiles and add to alkenes in a maimer similar to selenenyl halides (see equation 14), except that catalysis with Lewis acids is required in the case of unactivated alkenes. The selenocyanates are also popular reagents for the preparation of selenides from alcohols, and (8) from carboxylic acids, as indicated in Scheme 3. 

In the synthesis of (—)-lupinine (926) by Santos et al., (lR,2S,5R)-8-phenyhnenthol was used as the chiral auxiliary in controlling the stereochemical outcome of the reaction of the piperidine-containing carbamate 1042 with the 2-silyloxyfuran 1043 (Scheme 130). With trimethylsilyl triflate as Lewis acid catalyst and butyhnethylimidazolinium tetrafluorobo-rate as additive, an 80% yield was obtained as a 9.7 1 mixture in favor of threo-product (—)-1044. After hydrogenation of the double bond, treatment of the intermediate (—)-1045 with sodium methoxide effected rearrangement to the (R,R)-(- -)-l-hydroxyquinolizidin-4-one (- -)-1046 in 93% overall yield. Mitsunobu inversion of the alcohol to the (lS)-epimer (—)-1047 followed by alane reduction of the lactam afforded the quinolizi-din-l-ol (—)-1048. A second inversion at C-1 with cyanide produced the... 

The cyclic carbonate can then be copolymerized with cyclic anhydride to yield, with loss of carbon dioxide, a polyester of relatively high molecular weight. This copolymerization is initiated by a number of inorganic salts including sodium cyanide and potassium chloride, bases such as potassium hydroxide or sodium amide, and Lewis acids at 200°C. Presumably, the initiation begins with nucleophilic attack of an anion on the cyclic carbonate... 

The metabolism of cyanide has been studied in animals. The proposed metabolic pathways shown in Figure 2-3 are (1) the major pathway, conversion to thiocyanate by either rhodanese or 3-mercapto-pyruvate sulfur transferase (2) conversion to 2-aminothiazoline-4-carboxylic acid (Wood and Cooley 1956) (3) incorporation into a 1-carbon metabolic pool (Boxer and Richards 1952) or (4) combining with hydroxocobalamin to form cyanocobalamin (vitamin B12) (Ansell and Lewis 1970). Thiocyanate has been shown to account for 60-80% of an administered cyanide dose (Blakley and Coop 1949 Wood and Cooley 1956) while 2-aminothiazoline-4-carboxylic acid accounts for about 15% of the dose (Wood and Cooley 1956). The conversion of cyanide to thiocyanate was first demonstrated in 1894. Conversion of cyanide to thiocyanate is enhanced when cyanide poisoning is treated by intravenous administration of a sulfur donor (Smith 1996 Way 1984). The sulfur donor must have a sulfane sulfur, a sulfur bonded to another sulfur (e.g., sodium thiosulfate). During conversion by rhodanese, a sulfur atom is transferred from the donor to the enzyme, forming a persulfide intermediate. The persulfide sulfur is then transferred... 

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