1 -Methyl-4-acyl-1,2,5,6-tetrahydropyridines

TRIFLUORO-2-BUTYNOATE. C-Acylation of an enolate using methyl cyanoformate provides a convenient source of the a-carbometh-oxyoctalone, METHYL (la,4Ap,8Aa)-2-OXO-DECAHYDRO-l-NAPH-THOATE and represents a good example of generating jS-keto esters under mild conditions. The nitrone functionality is featured in a procedure which makes it in a single step from secondary amines and 6-METHYL-2,3,4,5-TETRAHYDROPYRIDINE N-OXIDE is the example described. Finally, the synthesis of phospholes l-PHENYL-2,3,4,5-TETRAMETHYLPHOS-PHOLE is described as an example of the versatility of zirconocene chemistry. 

An interesting synthesis of 5-amino-5-deoxy-DL-piperidinoses from l-acyl-1,2-dihydro-pyridines (21) has been reported (Scheme 2). The photochemical oxidation of (21) afforded the bicyclic peroxide (22) which on reduction gave the tetrahydropyridine (23). Hydroxylation of (23) afforded the cyanohydrin (24), which on hydrolysis and reduction afforded the methyl piperidinoses (25)-(27). (See also Vol. 12, p. 71.)... 

Reductions of aldehydes and ketones to alcohols proceed at slower rates with AERs in BH4 form than with NaBH4 in ethanol.a,j8-Unsaturated carbonyl compounds are reduced by BH4 in a gel AER to the allylic alcohols. Cyanoborohydride ion in a macroporous AER effects reductive aminations of ketones and ammonia to primary amines, reductive methylations of primary amines to the N,iV-dimethyl tertiary amines with aqueous formaldehyde, reductions of N-alkyl- and AT-acyl-pyridinium ions to tetrahydropyridines, and reductions of primary alkyl halides to alkanes. Nitroarenes are reduced to amines, the bromide of a-bromocarbonyl compounds is replaced by hydride, and 1,2-dibromoalkanes give alkenes by treatment with HFe(CO)4 in a macroporous AER. 

H " CHO also undergoes acid-catalyzed addition to olefinic substrates (Prins reaction). Treatment of the tetrahydropyridine derivative 138 with H " CHO in half-concentrated HCl provided racemic 3-hydroxy[ C]methyl product 139. a key intermediate in the synthesis of e.p. [7- C]paroxetine . Similarly, Prins-hydroxy[ C]methylation of acyl-... 

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