Ring‐Closing of 1,7‐ and 1,8‐Enynes of Propargylic O,O‐Acetals by Ruthenium‐Catalysed Intramolecular Metathesis

Abstract

Acyclic 1,7-and 1,8-enynes with the alkyne moiety directly connected to the asymmetric carbon of an ethyl acetal have been obtained in two steps from the corresponding aldehydes. Ring-closing metathesis of these enynes delivered the corresponding six-and seven-membered cyclic 1,3-dienes in

Enantioselective Access to Key Intermediates for Salvinorin A and Analogues

“…The following known compounds were isolated as pure samples and showed data matching those of reported compounds: (S)-2, [16] 3, [15] (Ϯ)-7b, [19a] 8a and 8b, [14] 9b. [31] General Procedure for ZnBr 2 -Catalyzed Diels-Alder Reactions: To a solution of freshly prepared sulfinylquinone (S)-2 (0.75-1.00 mmol, 1 equiv.)…”

“…[21] RCEM reactions leading to dienes 7a-d were performed using Grubbs 1st generation catalyst (1 mol-%), however, these conditions were totally ineffective for the RCEM of the precursors of 8a, 8b, 9a, and 9b. Finally, seven-membered ring based dienes 8a and 8b were obtained in good yields (80 and 70 %, respectively), [14] as well as the corresponding five-membered rings 9a and 9b (72 and 68 %, respectively) by reaction with Grubbs 2nd generation catalyst (5 mol-%) in dichloroethane under an ethylene atmosphere at 80°C. Returning to our model reaction (Scheme 2), we observed that cycloadduct 6 was stable at -20°C for several months (even years) and that it was possible to perform a desulfinylation using Raney-Ni in cold MeOH (-20°C) to give the corresponding cis-decalin 10 in 70 % yield.…”

“…We have recently published the preparation of dienes B with cyclic O,Oacetals (X = O, Y = OEt) -as precursors of the C(17) carbonyl group of salvinorin A or hemicetal group of salvinorin J [13] -by ring-closing metathesis of the corresponding 1,7-and 1,8-enynes of propargylic O,O-acetals. [14] Cycloaddition of these dienes with C (R 3 = Me), as well as of dienes B with a vinylic methyl group (R 4 = Me) with C (R 3 = H) will be disclosed in due course.…”

2-Vinyl Threoninol Derivatives via Acid-Catalyzed Allylic Substitution of Bisimidates

“…Alcohols 4a , b , e – l were prepared according to literature procedure . These compounds have been previously described in the literature: 1-(furan-3-yl)-2-methylpropan-1-ol ( 4a ), 1-(furan-3-yl)­pentan-1-ol ( 4b ), 1-(furan-3-yl)-2,2-dimethylpropan-1-ol ( 4e ), furan-3-yl­(phenyl)­methanol ( 4f ), , 1-(furan-3-yl)-2-phenylethanol ( 4g ), 1-(furan-3-yl)­ethanol ( 4h ), 1-(furan-3-yl)­but-3-en-1-ol ( 4i ), 1-(furan-3-yl)­pent-4-en-1-ol (11j) , 1-(furan-3-yl)­prop-2-en-1-ol ( 11k ), , 1-(furan-3-yl)­but-3-yn-1-ol ( 11l ) …”

Catalytic Light-Driven Strategy for Transforming Oximes to Carbonyls

“…49 (62 mg 78%) clear oil 1 1-Phenyl-3-buten-1-ol (5). 51 (Eluent: 10:1 hexane/ethyl acetate, 72 mg 67%) clear oil 1 (Z)-(2-Methoxyethenyl)benzene (6). 52 (Eluent: 10:1 hexane/ethyl acetate, 61 mg 62%) clear oil 1…”