Transannular Diels–Alder cyclization of substituted 13-membered trienes. An approach to the B.C.D.[6.6.5] rings of the 14β-hydroxysteroids

Abstract

Abstract:The transannular Diels-Alder strategy has been applied to three 13-membered macrocyclic trienes whose characteristics are: a cis-trans diene and a cis methoxymethyl en01 ether as the dienophile. The successful trials led to three 6.6.5 tricyles having a trans-syn-cis geometry exactly as in the B.C.D. rings of the 14P-hydroxysteroids.Key words: transannular, Diels-Alder, 14P-hydroxysteroids, 13-membered rings.Resum6 : La stratkgie de Diels-Alder transannulaire a CtC appliquke sur trois triknes macrocycliques B 15 membres dont les caractkristiques sont : un dikne cis-trans et un Cther d'Cnol rnCthoxymCthyle cis comme diknophile. Les essais positifs ont conduit ii trois tricycles 6.6.5 ayant une gComCtrie traizs-syn-cis exactement comme les cycles B.C.D. des 14P-hydroxystCro'ides.

Cascade Cyclization: An Easy Access to Highly Unsaturated Polycyclic Ring Systems through a Tandem Stille/[4 + 2] Reaction under Mild Conditions

“…In a first analysis, compound 4a could undergo a Stille macrocyclization and a subsequent transannular Diels−Alder (TADA) tandem reaction as described by Deslongchamps ,, and, even in some cases, on related 13-membered macrocycles …”

Efficient Ruthenium Carbenoid-Catalyzed Cross-Metathesis of Allyl Halides with Olefins

“…First, the crossmetathesis of 4a with allyl chloride in CH 2 Cl 2 was performed under N 2 at reflux for 6 h to give compound 5 in 75% yield (Table 1) with a greater than 20:1 E/Z ratio. Since the NMR signals for the vinyl protons were obscured, the E/Z identity was determined on the basis of 13 C NMR. For the E isomer, the allylic chloride-substituted carbon appeared at around δ 44 ppm, while the Z isomer appeared upfield by about 5 ppm (δ 38 ppm) due to the γ effect.…”

“…The monodecarboxylation of 17 proved to be problematic. Due to the presence of the carbohydrate moiety, common procedures involving DMSO at high temperatures failed. , Eventually, ester 17 was hydrolyzed first by refluxing in 2 M KOH/MeOH for 1 day and then decarboxylated in acetonitrile . Interestingly, the acetonitrile had to be degassed and the catalyst CuCl could not be used in more than 25 mol % .…”