2445-81-0Relevant articles and documents
A novel synthesis of coumarins employing triphenyl(α-carboxymethylene)phosphorane imidazolide as a C-2 synthon
Upadhyay, Puspesh K.,Kumar, Pradeep
scheme or table, p. 236 - 238 (2009/05/11)
A novel one-pot synthesis of coumarins via intramolecular Wittig cyclization from the reaction of phenolic compounds containing ortho-carbonyl group and triphenyl(α-carboxymethylene)phosphorane imidazolide is described.
Convenient synthesis of a simple coumarin from salicylaldehyde and wittig reagent. IV: Improved synthetic method of substituted coumarins
Takeuchi, Yasuo,Ueda, Norihiro,Uesugi, Koji,Abe, Hitoshi,Nishioka, Hiromi,Harayama, Takashi
, p. 217 - 224 (2007/10/03)
The reaction of salicylaldehydes (2) with Horner-Wadsworth-Emmons (HWE) or Ando-HWE reagents was attempted to afford intramolecular phosphonate derivatives (6). A new synthetic method for coumarins (1) was achieved by using protected 2.
Organophosphorus chemistry 32. 1 The reaction of vanillin, ortho-vanillin and piperonal with stabilized methylenetriphenylphosphoranes (wittig reagents)
Hafez, Taghrid S.,Henary, Maged M.,Mahran, Mohamed Refat H.
, p. 33 - 44 (2007/10/03)
Vanillin (1) and piperonal (3) reacted with ylidenetriphenylphosphoranes 4a-f in boiling toluene following the Wittig mechanism to give the ethylenes 5a-f and 7a-f. Similarly, ethylenes 8c-f were produced when ortho-vanillin (2) was allowed to react with 4c-f. The reaction of aldehyde (2) with the P-ylides 4a,b yielded the Wittig products 8a,b and 8-methoxycoumarin (10). Triphenylphosphine oxide (TPPO, 6) was isolated and identified in all cases. The mechanism for formation of 10 was discussed. Structural reasonings for all new compounds were based upon compatible elementary as well as spectroscopic (IR, 1H-NMR and MS) measurements.
A Convenient Synthesis of a Simple Coumarin from Salicylaldehyde and Wittig Reagent (I): A Synthesis of Methoxy- and Hydroxycoumarins
Harayama, Takashi,Katsuno, Keiko,Nishioka, Hiromi,Fujii, Masako,Nishita, Yoshitaka,et al.
, p. 613 - 622 (2007/10/02)
Reaction of methoxy- and hydroxysalicylaldehydes (1) with phosphorane in diethylaniline under reflux gave only coumarins (3) in high yields except for 3-methoxysalicylaldehyde (1b).It was clarified that methoxy group(s) at C4 and C6 on 1 facilitated the formation of 3.
A convenient synthesis of a simple coumarin
Ishii,Kaneko,Miyazaki,Harayama
, p. 3100 - 3102 (2007/10/02)
Reaction of salicylaldehydes (1) with carbethoxymethylenephosphorane in diethylaniline under reflux gave coumarins (3) in excellent yields. Methoxy substituent at C'4 on salicylaldehyde (1) facilitated the formation of coumarin from trans-cinnamate (2), which is first prepared by reaction of 1 with Wittig reagent.
New Syntheses of Coumarins
Panetta, Jill A.,Rapoport, Henry
, p. 946 - 950 (2007/10/02)
New, versatile coumarin syntheses have been developed which are based on the Claisen rearrangement of allylic or propargylic aryl ethers in which the allylic or propargylic α-carbon is further oxygenated.One proceeds by first ester exchange to the aryl dialkyl orthoacrylate which then thermally rearranges.Hydrolytic treatment gives the o-hydroxydihydrocinnamic acid from which the coumarin is obtained by ring closure and dehydrogenation.In parallel fashion, an orthopropiolate may be used, eliminating the dehydrogenation step.These processes have the adventage ofavoiding the drastic acid conditions and orientation limitations of previous coumarin syntheses.They have been applied to syntheses in good yields of coumarins obtainable by previous methods in very poor yield or not at all.
