Synthesis of aldehydes from dihydro-1,3-oxazines

2-(Arylsulfinylmethyl)oxazinanes: chiral carbonyl equivalents. Application to the asymmetric synthesis of 1,2,3,4-tetrahydro-β-carbolines

“…trans-selectivity was favoured when the reaction was run at low temperature. The cis and trans isomers were distinguished as reported from the 13 C chemical shifts of the C-1 (cis: downfield, trans: upfield) 21 and also from the benzylic…”

Asymmetric synthesis towards (3Z,6R)-3-methyl-6-isopropenyl-3,9-decadien-1-yl acetate, a component of the California red scale pheromone

“…The uldimirze route The 1,4-addition of Grignard reagents to chiral a,Punsaturated aldimines prepared from &,@unsaturated aldehydes and chiral tert-butyl 2-amino-3,3-dimethylbutyrate (26) has been demonstrated (21) to give chiral P-substituted aldehydes in greater than 95% ee. Since the key intermediate (3) in the synthesis of 1 is a P-substituted aldehyde, we decided to attempt this method for the preparation of 3.…”

“…Many procedures described in the literature exist for the synthesis of a,P-unsaturated aldehydes from a simple aldehyde, but attempts to prepare 18 by various methods (23)(24)(25) were either unsuccessful or gave impure 18 in low yield. Finally, treatment of 6 with 2,4,4,6-tetramethyl-5,6-dihydro-l,3-oxazine (23) according to the procedure of Meyers et al (26) gave the alcohol adduct (24). Reduction of 24 with sodium borohydride gave the tetrahydro-l,3-oxazine (25), which on mild acid hydrolysis gave 18 in 37% overall yield (Scheme 4).…”

“…Treatment of the a,P-unsaturated aldehyde 18 with racemic tert-butyl 2-amino-3,3-dimethylbutyrate (26) For personal use only. racemic mixture of 3 with its enantiomer or optically active 3 in a 43-50% yield.…”

2-oxazolinas quirais: algumas aplicações como indutores de assimetria em reações orgânicas

“…A partir do final da década de 60, a exemplo do que vinha ocorrendo com outros heterociclos como as ditianas 2 , oxazinas 3 e isoxazóis 4 , a reatividade das 2-oxazolinas começou a ser mais intensamente investigada, abrindo boas perspectivas para um crescente emprego de tais compostos em síntese orgânica [5][6][7][8] . Neste artigo serão abordadas algumas reações que se processam com estereosseletividade empregando 2-oxazolinas quirais como indutores de assimetria, além de uma breve introdução sobre métodos de obtenção de 2-oxazolinas e a discussão de algumas de suas propriedades, tendo em vista que a utilização de tais sistemas, em nível nacional, tem sido pouco explorada.…”