A new prenylation method based on the reaction of catalytically generated potassium dienolate of prenal with α,β-unsaturated aldehydes is described. The reaction is highly regioselective, via a γ-1,2-addition, and provides an efficient route to retinal.
A method for preparing dehydro-cyclofarnesal from dehydro-farnesal by cyclization in the presence of an acid may include the dehydro-farnesal being obtained from the farnesal by dehydrogenation and may further includes the cyclization being carried out in the presence of an acid selected from Lewis acids, Bronstedt acids, and zeolites. The synthesis of vitamin A using this method further includes the conversion of dehydro-cyclofarnesal into vitamin A.
A method for preparing dehydro-cyclofarnesal from dehydro-farnesal by cyclization in the presence of an acid may include the dehydro-farnesal being obtained from the farnesal by dehydrogenation and may further includes the cyclization being carried out in the presence of an acid selected from Lewis acids, Bronstedt acids, and zeolites. The synthesis of vitamin A using this method further includes the conversion of dehydro-cyclofarnesal into vitamin A.
一种在酸存在下通过环化从脱氢-法呢醛制备脱氢-环法呢醛的方法可包括通过脱氢从法呢醛中获得脱氢-法呢醛,并可进一步包括在选自路易斯酸、勃朗斯特酸和沸石的酸存在下进行环化。使用这种方法合成维生素 A 还包括将脱氢环法尼萨转化为维生素 A。
Regioselective addition of the prenal potassium dienolate onto α,β-unsaturated aldehydes. A short access to polyenaldehydes
The potassium dienolate of prenal obtained by treatment of the corresponding dienoxysilane with tBuOK was reacted with enaldehydes. In all cases a gamma-specific reaction occurs. According to the reaction conditions gamma;1,2 or a gamma;1,4 coupled product was selectively obtained with enals. The gamma;1,2 reaction provided an efficient prenylation procedure. A short two-step synthesis of retinal is described. (C) 1998 Elsevier Science Ltd. All rights reserved.