Tetrabutylammonium cyanide catalyzes the addition of TMSCN to aldehydes and ketones

Issue in Honor of Prof. Enrique Meléndez ARKIVOC 2004 (iv) 94-99 al.4 where the formation of bezenic derivative 4 was observed when using a molar ratio 1: TMS- CN: Bu4NCN = 1: 18.4: 1 (Scheme 1). Br Br Br TMSCN (1.0 eq) OTMS OTMS MeO O MeO MeO CN CN Bu4NCN (0.1 eq) O CH2Cl2, 0ºC, 15 min O O Br Br Br 1 23 TMSCN, Bu4NCN CH2Cl2 (ref. 4, 54%) Br MeO OH OH Br CN 4 Scheme 1 In the context of these findings, two comments should be made: i) the reaction of 1 with TMSCN in the absence of the ammonium salt resulted in the recovering of unaltered starting material; and ii) to the best of our knowledge, only an isolated report describing the use of Bu4NCN as catalytic agent for the O-TMS-cyanosilylation of 3-pentanone (84% isolated yield) has been previously reported.5 On the basis of these considerations, we decided to explore the scope and limitations of the use of the system TMSCN/Bu4NCN(cat.) for the O-TMS-cyanosilylation of other spiroepoxycyclohexadienones and also for the same reaction using some representative carbonyl derivatives as starting materials. The results of the OTMS-cyanosilylation of a variety of spiroepoxycyclohexadienones (Scheme 2) and some other representative carbonyl compounds (Scheme 3) are quoted in Tables 1 and 2 respectively. R1 R1R1 TMSCN (1.0 eq) OTMS OTMS R2 R2 O R2 CN CN Bu4NCN (0.1 eq) O CH2Cl2, 0ºC, 15 min O O R3 R3 R3 R4 5 -7 R4 8 -10 R4 Scheme 2 ISSN 1424-6376 Page 95 ©ARKAT USA, Inc