Construction of Highly Substituted Stereodefined Dienes by Cross‐Coupling of α‐Allenic Acetates

Abstract

The assembly of highly substituted dienes remains a challenge for organic chemistry. This work represents a strategy for the construction of highly substituted 1,3-dienes by means of a Tsuji-Trost cross coupling between α-allenic acetates and organozinc reagents. The reaction is high yielding, and installs a trisubstituted olefin with E/Z selectivities up to 95:5 favoring the (E) product. A cheap, commercially available palladium precatalyst and a ligand are used to control the E/Z selectivity. Furthermore, an interesting reversal in selec-

CuI‐Catalyzed Synthesis of Functionalized Terminal Allenes from 1‐Alkynes

“…2‐Phenyl‐3,4‐pentadien‐2‐ol (2m): The reaction of CuI (191.2 mg, 1.00 mmol), paraformaldehyde (481.4 mg, 16.03 mmol), 1m (1.4657 g, 10.03 mmol), and i Pr 2 NH (2.0 mL, d = 0.716 g mL –1 , 1.432 g, 14.15 mmol) in dioxane (15 mL) afforded 2m 11f (1.3540 g, 84 %) after purification (eluent for chromatography: petroleum ether/ethyl acetate, 10:1) as a liquid. 1 H NMR (300 MHz, CDCl 3 ): δ = 7.49 (d, J = 7.8 Hz, 2 H, ArH), 7.33 (t, J = 7.2 Hz, 2 H, ArH), 7.23 (t, J = 6.9 Hz, 1 H, ArH), 5.54 (t, J = 6.4 Hz, 1 H, C=CH), 5.00–4.85 (m, 2 H, C=CH 2 ), 2.30 (s, 1 H, OH), 1.64 (s, 3 H, CH 3 ) ppm.…”

Synthesis and Structural Characterization of a Series of New Chiral‐at‐Metal Ruthenium Allenylidene Complexes

“…( R )‐1,1′‐Binaphthyl‐2,2′‐diol [( R )‐binol] (Strem), catechol (Fisher), phosphorus trichloride (PCl 3 ), N ‐methyl‐2‐pyrrolidinone (Acros), ( R )‐2‐methylpyrrolidine (Aldrich), 1,1‐diphenyl‐2‐propyn‐1‐ol (Aldrich), 2‐phenyl‐3‐butyn‐2‐ol (Aldrich), (Et 3 O)PF 6 (Aldrich), Celite® (Aldrich), tert ‐butyl methyl ether (Aldrich), and other materials were used as received. ( R )‐binol‐ N , N ‐dimethylphosphoramidite ( 5a ),21a ( R )‐binol‐ N , N ‐dibenzylphosphoramidite ( 5b ),21c ( R , S )‐binol‐ N ‐benzyl‐ N ‐α‐methylbenzylphosphoramidite ( 5c ),33 2‐(2‐furyl)‐3‐butyn‐2‐ol ( 14c ),34 bis(4‐fluorophenyl)‐3‐propyn‐2‐ol ( 14d ),35a 2‐(4‐methoxyphenyl)‐3‐butyn‐2‐ol ( 14e ),35b and [RuCl(Ind)(PPh 3 ) 2 ] ( 11 )28 were synthesized according to literature procedures.…”

Dendralenes Branch Out: Cross‐Conjugated Oligoenes Allow the Rapid Generation of Molecular Complexity

“…[79] Several other-albeit isolated-examples of cross-coupling reactions involving 1,2-butadien-4-yl electrophiles to form [3]dendralenes have been reported. [69,80] A particularly interesting variation involves the palladium(0)catalyzed Mizoroki-Heck reaction of 2-bromostyrene (85) with dimethylallene (87) to form 2-methyl-4-phenyl [3]dendralene (88). [81] Double cross-coupling reactions have also been used successfully for the synthesis of many dendralene derivatives.…”