ChemInform Abstract: THE PRINS‐FORMALDEHYDE CONDENSATION ON MYRCENE AND SIMPLE DERIVATIVES

Abstract

Die säurekatalysierte Kondensation der Titelverbindung (II) mit Paraformaldehyd in 1,4‐Dioxan ergibt das Produkt (I), während in Methylenchlorid/Sn‐tetrachlorid die Produkte (III)‐(V) erhalten werden.

A Concise Synthesis ofrac‐Ambrox®viathe Palladium(0)‐Catalyzed Carboalkoxylation of an Allylic Ammonium Salt, as Compared to a Formaldehyde HeteroDiels–AlderApproach

“…[34]. 4 This compound exhibits a lemon, rosy, citronellol, geraniol, and citral scent, as well as the following 13 C-NMR analytical data: 135.6 (s); 131.7 (s); 124.0 (d); 119.6 (d); 65.6 (t); 64.4 (t); 37.1 (t); 28.6 (t); 25.9 (t); 25.7 (q); 17.7 (q). B.p.…”

“…of 96 % H 2 SO 4 in MeOH/THF to afford in 24-25 % yield 34c as a 84 : 16 to 80 : 20 mixture of (E/Z) stereoisomers after 48 h at 60°C under 60 bars of CO. 24[91] In our hands (Scheme 4), farnesyldiethylamine 29b likewise afforded the ethyl ester 34b in 15 % yield as a 76:24 (E/Z) mixture (EtI, EtOH, 60°C, 60 bar CO, 0.01 mol-equiv. Pd(PPh 3 ) 4 ). [92] The chemical yield increased to 32 % when a 1 : 1 mixture of EtOH/THF was used.…”

“…The simple conditions previously reported by Margot and Schlosser for the 'formal' hetero DielsÀ Alder reaction between paraformaldehyde and myrcene 1, [1][2][3][4] encouraged us to extend this reaction to other dienes, in particular, to the now readily available farnesene 2 [5][6][7][8] (Scheme 1), δ-pyronene 3 1[9-18] (Scheme 2), the known bicyclic diene 4, 2 [22][23][24][25][26][27][28][29][30][31][32] and 2,3-dimethylidenenorbornane 5, 3[35-39] as well as to the unreported diene 6 (Scheme 3). Our simple basic concept consisted of cleaving the resulting dihydropyran allylic CÀ O bond via a Birch reduction, [3,40] followed by cyclization of the correspond-ing homoallylic alcohol under acidic conditions, [41][42][43][44][45] in order to create new tetrahydrofuran derivatives, which might possess amber-like scents.…”