Synthesis of 4-alkyl-4-(4-methoxyphenyl)cyclohex-2-en-1-ones and 5-alkyl-5-phenyl-1,3-cyclohexadienes from bis(tricarbonylchromium)-coordinated biphenyls

Abstract

6: 6-Biphenyl) [Cr(CO)3] 2 and (T)6:i)6-4,4'-dimethoxybiphenyl) [Cr(CO)3] 2 were chemically reduced with lithium anthracenide or lithium naphthalenide in THF to generate stable dianions having a (7j5-cyclohexadienylidene)2[Cr(CO)3]2 structure. The (j?5-cyclohexadienylidene)2[Cr(CO)3]2 dianion reacted cleanly with electrophiles such as H20, D20, benzyl tosylate, ally! tosylate, methyl iodide, and primary alkyl bromides, tosylates, and sulfates in a highly stereoselective and regioselective manner to form [M-6-substituted-6-(7j6-phenyl)(l-5-jj5)-cyclohexadienyl]bis(tricarbonyIchromium) anions. Direct oxidation of the [>i-6-alkyl-6-(i76-phenyl)(1-5-775)-cyclohexadienyl]bis(tricarbonylchromium) anions with iodine yielded 2-alkylbiphenyls, whereas protonation with trifluoroacetic acid (TFAA) generated [5-alkyl-5-(7?6-phenyl)-l,3-cyclohexadiene]tricarbonylchromiums. The [5-alkyl-5-(r;6-phenyl)-l,3-cyclohexadiene]tricarbonylchromiums were oxidized by I2 or air to generate the free 5-alkyl-5-phenyl-1,3-cyclohexadienes without rearrangement and in excellent yields. Chemical reduction of (j)6:t)6-4,4'-dimethoxybiphenyl)[Cr(CO)3]2 at -78 °C with lithium naphthalenide yielded a dianion which reacted with methyl triflate, ethyl triflate, or allyl tosylate. Workup with TFAA and I2 resulted in the formation of 4-alkyl-4-(4-methoxyphenyl)cyclohex-2-en-1 -one products in fair yields. Isolation of 4-al!yl-4-(4-methoxyphenyl)cyclohex-2-en-1 -one represents a formal synthesis of the synthetically important Sceletium alkaloid, O-methyljoubertiamine.be induced, generating the trans-5,6-disubstituted-cyclohexadiene,

Synthesis of Unsymmetrical Biaryls by Palladium-Catalyzed Cross Coupling Reactions of Arenes with Tetrabutylammonium Triphenyldifluorosilicate, a Hypervalent Silicon Reagent

“…Entry 17, 2-Methylbiphenyl: TLC R f = 0.59 (10% Et 2 O/pentane); IR (CCl 4 ) 3063 (m), 3025 (m), 2963 (w), 2925 (m), 2869 (w), 1600 (s), 1550 (s); 1 H NMR (CDCl 3 ) δ 2.27 (s, 3H), 7.22−7.44 (m, 9H); 13 C NMR (CDCl 3 ) δ 21.9, 124.6, 127.5, 128.3, 129.0, 138.7, 141.6; LRMS 169 ((M + 1), 20), 168 ((M + ), 100), 167 (85), 165 (41), 153 (34), 152 (28); HRMS (EI) calcd for C 13 H 12 168.0939 (M + ), found 168.0937. The IR, 1 H NMR, and HRMS are identical to the spectral data found in ref .…”

“…+ ), found 168.0937. The IR, 1 H NMR, and HRMS are identical to the spectral data found in ref15.General The triflates were prepared using a modification of a procedure in Synthesis.11 …”