Process for the preparation of furan compounds

A process for the preparation of furan compounds, the process comprising the step of:

• carrying out a reaction of a carbonyl compound represented by following Formula (1) in the presence of a catalytic palladium compound (A):
• wherein R1 represents an hydrogen atom, substituted or unsubstituted hydrocarbon groups including aliphatic hydrocarbon groups having about one to about twenty carbon atoms, aromatic hydrocarbon groups having about six to about twenty carbon atoms, alicyclic hydrocarbon groups having about three to about twenty carbon atoms, bridged hydrocarbon groups, haloalkyl groups having about one to about six carbon atoms, heterocyclic groups;
• alkoxy groups having about one to about ten carbon atoms, aryloxy groups, aralkyloxy groups, cycloalkyloxy groups, and acyloxy groups having about one to about ten carbon atoms, acyl groups, carbonyl-protected acyl groups, substituted oxycarbonyl groups including alkoxy-carbonyl groups having about one to about six carbon atoms in the alkoxy moiety, aryloxycarbonyl groups, aralkyloxycarbonyl groups, and cycloalkyloxycarbonyl groups, substituted or unsubstituted carbamoyl groups, cyano groups, or sulfur acid ester groups ;
• and
• R2 represents an hydrogen atom, substituted or unsubstituted hydrocarbon groups having about one to about twenty carbon atoms, aromatic hydrocarbon groups having about six to about twenty carbon atoms, alicyclic hydrocarbon groups having about three to about twenty carbon atoms, bridged hydrocarbon groups and haloalkyl groups having about one to about six carbon atoms, or heterocyclic groups, wherein R1 and R2 may be combined to form a ring with adjacent two carbon atoms, with an unsaturated compound represented by following Formula (2):
• wherein R5 represents hydrogen atom, a halogen atom, hydroxyl group, or an organic group,
• wherein when R5 is hydrogen atom, R3 is any of hydrogen atom, a halogen atom, hydroxyl group and an organic group,
• and when R5 is a halogen atom, hydroxyl group or an organic group, R3 is a leaving group wherein leaving group is defined as a group that leaves as R3H during the reaction, and
• wherein R4 is an electron-withdrawing group,
• to yield a furan compound represented by following Formula (3):
• wherein R3′represents R3, R5 or hydrogen atom;
• and R1, R2, R3, R4, are R5 are as defined above.

A process for the preparation of furan compounds, the process comprising the step of:

• carrying out a reaction of a carbonyl compound represented by following Formula (1) in the presence of a catalytic palladium compound (A) and a promoter (B):
• wherein each of R1 and R2 represents an hydrogen atom or a hydrocarbon group having one to about twenty carbon atoms, wherein R1 and R2 may be combined to form a ring with adjacent two carbon atoms, or a multimer of carbonyl compounds, or a carbonyl protected derivative that yields the same reaction product as the carbonyl compound represented by Formula (1) with an unsaturated compound represented by following Formula (2):
• wherein R5 represents a hydrogen atom, a halogen atom, hydroxyl group, or a group having one to twenty carbon atoms selected from a group consisting of hydrocarbon group, heterocyclic group, substituted oxy group, N-substituted amino groups, acyl groups and carbonyl-protected derivatives thereof, substituted oxycarbonyl groups, carboxyl group unprotected or protected by protecting groups, substituted or unsubstituted carbamoyl groups, cyano group, substituted or unsubstituted iminoalkyl group, sulfur acid ester group, and a group containing two or more of these groups combined with each other,
• wherein when R5 is hydrogen atom, R3 is any of a hydrogen atom, a halogen atom, hydroxyl group or a group having one to twenty carbon atoms selected from a group consisting of hydrocarbon group, heterocyclic group, substituted oxy group, N-substituted amino groups, acyl groups and carbonyl-protected derivatives thereof, substituted oxycarbonyl groups, carboxyl group unprotected or protected by protecting groups, substituted or unsubstituted carbamoyl groups, cyano group, substituted or unsubstituted iminoalkyl group, sulfur acid ester group, and a group containing two or more of these groups combined with each other,
• and when R5 is a halogen atom, hydroxyl group or a group having one to twenty carbon atoms selected from a group consisting of hydrocarbon group, heterocyclic group, substituted oxy group, N-substituted amino groups, acyl groups and carbonyl-protected derivative thereof, substituted oxycarbonyl groups, carboxyl group unprotectcd or protected by protecting groups, substituted or unsubstituted carbamoyl groups, cyano group, substituted or unsubstituted iminoalkyl group, sulfur acid ester group, and a group containing two or more of these groups combined with each other R3 is a leaving group, wherein leaving group is defined as a group that leaves as R3H during the reaction, and
• wherein R4 is an electron-withdrawing group,
• or a compound selected from a group consisting of 3,3-dialkoxypropionic ester, 3,3-dialkoxypropionitrile, 3,3-dialkoxypropionaldehyde, beta-ketoacetal and beta-diketone,
• to yield a furan compound represented by following Formula (3):
• wherein R3′ represents R3, R5 or hydrogen atom;
• and R1, R2, R3, R4, are R5 are as defined above,
• wherein the promoter (B) comprises a heteropolyacid or a salt thereof (B1) comprising an element selected from phosphorus and silicon and at least one element selected from vanadium, molybdenum and tungsten as constitutional elements;
• or
• a mixture of oxoacids and/or salts thereof (B2) containing as a whole, an element selected from phosphorus and silicon and at least one element selected from vanadium, molybdenum, and tungsten.