Solvent-free catalysed synthesis of tetrahydropyran odorants: the role of SiO

Abstract

Foi desenvolvido um procedimento eficiente e ecologicamente amigável para a promoção da ciclização de Prins em ausência de solventes orgânicos baseado na maceração de um aldeído e um álcool alílico em presença de quantidade catalítica de p-TSA disperso em sílica gel. Por esse procedimento foram sintetizadas as fragrâncias comerciais Florol ® e Clarycet ® , em uma e duas etapas sintéticas respectivamente.An efficient, green and solvent-free catalysed Prins-cyclization reaction based on the simple grinding of an aldehyde and a homoallylic alcohol in the presence of catalytic amount of p-TSA on silica gel is reported. By this protocol were synthesized tetrahydropyran odorants including commercial Florol ® and Clarycet ® , in one and two steps respectively.

Acid‐modified Halloysite Nanotubes as a Stereoselective Catalyst for Synthesis of 2H‐Chromene Derivatives by the Reaction of Isopulegol with Aldehydes

“…A high pharmaceutical potential and low toxicity of these substances resulted in a considerable interest in the synthesis of new chromene derivatives . Recently, it has been shown, that in catalytic condensation of a natural allyl alcohol (−)‐isopulegol (I) with aldehydes, substituted octahydro‐2 H ‐chromen‐4‐ol (III) as 4 R ‐ and 4 S ‐diastereomers was formed along with a dehydration product IV (Scheme ). Different catalysts such as I 2 , p ‐toluenesulfonic acid, BF 3 ⋅Et 2 O, zeolites, clays were used in this reaction .…”

“…It is known that compounds with a chromene (benzopyran) scaffold have a broad spectrum of biological activity . A high pharmaceutical potential and low toxicity of these substances resulted in a considerable interest in the synthesis of new chromene derivatives . Recently, it has been shown, that in catalytic condensation of a natural allyl alcohol (−)‐isopulegol (I) with aldehydes, substituted octahydro‐2 H ‐chromen‐4‐ol (III) as 4 R ‐ and 4 S ‐diastereomers was formed along with a dehydration product IV (Scheme ).…”

“…Recently, it has been shown, that in catalytic condensation of a natural allyl alcohol (−)‐isopulegol (I) with aldehydes, substituted octahydro‐2 H ‐chromen‐4‐ol (III) as 4 R ‐ and 4 S ‐diastereomers was formed along with a dehydration product IV (Scheme ). Different catalysts such as I 2 , p ‐toluenesulfonic acid, BF 3 ⋅Et 2 O, zeolites, clays were used in this reaction . A relatively high 4 R /4 S ratio (9.0) with overall yields of 70–88 % were observed in condensation of isopulegol (obtained by cyclization of R ‐citronellal) with aromatic aldehydes at −78 °C using scandium triflate .…”

The Prins Reaction in the Fragrance Industry: 100th Anniversary (1919–2019)

“…Unsaturated precursors of Doremox ® ( 9 ) and Rose oxide ( 11 ) were prepared in an enantiomerically pure form by employing a novel organocatalysis synthesis . Clarycet ( 7 ) and Florol ® ( 8 ) were prepared through solvent‐free procedures . Some of the fragrance ingredients reported herein can be prepared through alternative chemical routes.…”

Stereoselective hydrogenation of 3-acyl-substituted 2- (trifluoromethyl)-2H-chromen-5-one and chromane scaffolds in NaBH4 /ethanol medium

“…For this reason, there is a clear growth in the employing of some of them as flavor and perfume compounds in certain odorants. 1 On the other hand, the reducing agent sodium borohydride is commonly used for reduction of unsaturated carbonyl compounds, is becoming a standard method in both academic and industrial laboratories. 2 In this context, we describe a synthesis of a new series of substituted octahydrochromenone derivatives (2) from the 2-trifluoromethyl-2Hchromenones (1) and one example of 3,4-dihydro-2H-chromane (4) from the respective 2-(trifluoromethyl)chromane (3), employing sodium borohydride/ethanol as an efficient, straightforward and selective reductive reaction medium for these types of heterocyclic compounds.…”