Catalytic Asymmetric [4+2]-Cycloaddition of Dienes with Aldehydes
作者:Luping Liu、Hyejin Kim、Youwei Xie、Christophe Farès、Philip S. J. Kaib、Richard Goddard、Benjamin List
DOI:10.1021/jacs.7b08357
日期:2017.10.4
Despite its significant potential, a general catalytic asymmetric [4+2]-cycloaddition of simple and electronically unbiased dienes with any type of aldehyde has long been unknown. Previously developed methodologies invariably require activated, electronically engineered substrates. We now provide a general solution to this problem. We show that highly acidic and confined imidodiphosphorimidates (IDPis)
A process for producing a 5-arylpentanol of formula (2):
1
wherein R
1
represents an aryl group which may be substituted with one or two or more of an alkyl or alkoxy group and has 6 to 12 carbon atoms in total, R
3
represents a hydrogen atom, or an alkyl or alkenyl group of 1 to 6 carbon atoms, and R
4
represents R
2
defined below when R
2
is a monovalent group or represents R
2
H when R
2
is a divalent group, which comprises effecting hydrogenolysis of a pyran compound of formula (1):
2
wherein, R
1
and R
3
are as defined above, R
2
represents a hydrogen atom, an alkyl or alkenyl group of 1 to 6 carbon atoms, or an alkylidene or alkenylidene group of 1 to 6 carbon atoms, and a dotted line represents a possible bond and any one of the three bonds represented by dotted lines and solid lines is a double bond, in the presence of one or more catalysts selected from (a) a catalyst carrying two or more elements selected from noble metals in Group VIII in the periodic table and (b) an acid type palladium-supporting catalyst. 5-arylpentanols can be prepared in a high yield with low production of hydrocarbons without causing a problem with regard to corrosion of process equipment.
To provide a simple process for economically preparing a dihydropyrane compound at a high productivity and a high reaction yield. To use a compound selected from the group consisting of a base and a compound (VIII) having a weaker coordination power to the Lewis acid than the aldehyde compound and having an activity to dissolve the Lewis acid, coordinated by the compound (VIII), in a solvent as a co-catalyst in reacting aldehyde with a diene compound in the presence of a Lewis acid to prepare a 5,6-dihydro-2H-pyrane compound represented by formula (III): ##STR1## in which R.sup.1 represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, aryl group which may be substituted with alkyl group, having 6 to 12 total carbon atoms; R.sup.2 and R.sup.3 represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.
A compound having the structure (A) where R1 is C1 to C5 alkyl, and R2 to R5 are independently selected from H and methyl, having a strong odour and for use as a perfumery ingredient, particularly in Muguet accords/fragrances, is provided.
The invention provides a process for the preparation of 5,6-dihydro-2H-pyran derivatives, wherein an aldehyde of formula I:
wherein R₁ represents an alkyl, cycloalkyl, aralkyl, alkaryl or aryl group having at most 15 carbon atoms and a diene of formula II:
wherein R₂ and R₃ represents a hydrogen atom or an alkyl group having 1-6 carbon atoms are reacted in a Diels-Alder-type reaction under the influence of an inorganic Lewis acid catalyst, producing a compound of formula III wherein R₁-R₃ have the meaning given above.
Preferably R₁ represents a 1-6 carbon atom alkyl group, a phenyl group or an o-, m- p-tolyl group. Isoprene or 2-methyl-1,3-pentadiene is preferably used as the diene. The preferred catalyst is AlCl₃ or SnCl₄ and an organic nitro compound may be used as the co-catalyst.