Arylation cyclohexenes

The total synthesis of ( )-lycoricidine (214) from the aryl cyclohexene 272, which was accessed by a Diels-Alder reaction of the carbinol 46, has been... 

A synthesis of the alkaloid narseronine 53 that highlights yet another novel mode of cyclisation of arylated cyclohexenes derived from compound 67 is shown Scheme 9 (White et al., unpublished work [45]). Thus, nitrile 73 (generated from precursor 67 during the course of our synthesis of the lycorine degradation product 79 as shown in Scheme 6) was reduced with dihydrogen in the presence of Raney-cobalt and the resulting primary amine was then protected as the corresponding... 

The allylic carbamate 193 formed as shown in Scheme 17 can be exploited in the synthesis of a pancratistatin analogue. Thus, Suzuki-Miyaura cross-coupling of this carbamate with aryl boronic acid 61 (Scheme 18) afforded the expected arylated cyclohexene 200 (87%) that upon sequential treatment with diborane, alkaline hydrogen peroxide, aqueous acid then acetic anhydride gave the triacetate 201 (42%). Subjecting this last compound to the Bischler-Napieralski reaction... 

John McMurry (Cornell University) described a synthesis of 125 that begins with preparation of aryl cyclohexene 126 (see Problem 21). Hydroboration-oxidation of this alkene gave ketone 127. 

The reaction of an alicyclic enamine with benzyne intermediate yields simple arylation products and/or 1,2-cycloaddition products, depending upon the reaction conditions 102). This is illustrated by the reaction of l-(N-pyrrolidino)cyclohexene with benzyne (86) (obtained from fluoro-benzene and butyl lithium or o-bromofluorobenzene and lithium amalgam), which produces benzocyclobutene 87 102). 

Eine einfache Methode zur Uberfiihrung von 1-Aryl-l-alkenen bzw. a-Aryl-alkoholen zu Aryl-alkanen stellt die Transferhydrierung mit Cyclohexen/Aluminiumchlorid/Pal-ladium-Kohle dar (naheres s. hierzu Bd. IV/lc, S.73f.)5 ... 

The Heck reaction has been applied to synthesis of intermediates and in multistage syntheses. Some examples are given in Scheme 8.9. Entries 1 and 2 illustrate both the (3-regioselectivity and selectivity for aryl iodides over bromides. Entries 3 and 4 show conditions that proved favorable for cyclohexene. These examples also indicate preferential syn Pd-H elimination, since this accounts for formation of the 3-substituted cyclohexene as the major product. 

In Entry 9, the initial reaction involves 5-exo addition of the aryl radical to the more-substituted end of the cyclohexene double bond, followed by a 6-endo addition to the phenylthiovinyl group. The reaction is completed by elimination of the phenylthio radical. The product is an intermediate in the synthesis of morphine. 

R1 = Bu, (CH2)2CI, cyclohexen-1-yl, (CH2)2OPiv or CH2OBut R2 = aryl or alkyl group R3 = alkyl or aryl group... 

R1 = aryl, alkyl, benzyl, PhCH2OCH2, (EtO)2CHCH2, (EtO)2CHCH2CH2 or 2-aminoethyl R2 = aryl, alkyl, cyclohexen-1-yl or (EtO)2CH E+ = l2, C02, CIC02Me, HC02Et, PhCHO, PhNCO, trichloromethyl carbonate, or carbamoyl chloride... 

HEXAHYDRO - 4a,5 - DIMETHYL - 2(3H) - NAPHTHALE-NONE and 2-TRIMETHYLSILYLOXY-1,3-BUTADIENE AS A REACTIVE DIENE DIETHYL trans -4-TRIMETHYL-SILYLOXY-4-CYCLOHEXENE-1,2-DICARBOXYLATE. Sulfur substitution also continues to be of high interest, and three preparations on sulfide synthesis are included BENZYL SULFIDE DIALKYL AND ALKYL ARYL SULFIDES NEOPENTYL PHENYL SULFIDE and UNSYMMETRICAL DIALKYL DISULFIDES sec-BUTYL ISOPROPYL DISULFIDE. 

Ni(II) complexes of cyclam and oxocyclam derivatives catalyze the epoxidation of cyclohexene and various aryl-substituted alkenes with PhIO and NaOCl as oxidants, respectively. In the epoxidation catalyzed by the Ni(II) cyclam complex using PhIO as a terminal oxidant, the high-valent nickel- complexes (e.g., LNiin-0, LNi=0, LNiin-0-... 

A study of the scope of the reaction has shown that mono- and disubstituted alkenes and, particularly, aryl-substituted alkenes are the best substrates. Various limitations have been noted, some not unexpected (sensitivity to steric effects), others quite surprising (complex reactivity of cyclohexenes). Nevertheless, the exceptionally high stability of the reagent should make it available from the shelf, and in appropriate cases its use is to be considered as an alternative to the Simmons-Smith reaction. 

Photolysis of thiatriazoles was first described by Kirmse,25 who found that aryl cyanides, aryl isothiocyanates, and sulfur are formed on irradition of 5-arylthiatriazoles with UV light. Recently Okazaki et al.n reported the formation of sulfur atoms on irradiation of thiatriazoles. Photolysis of 5-phenylthiatriazole (A lax= 280 nm, e — 10800)25 in the presence of cyclohexene yielded cyclohexene episulfide. Cyclohexene thiols were not formed this was taken as an indication that the reactive species is a triplet sulfur atom. Tetramethylethylene behaves similarly.22... 

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