Carbamates nickel-catalyzed coupling

Aryl carbamates are also reactive toward nickel-catalyzed coupling.270 Since the carbamates can be readily prepared from phenols, they are convenient starting materials. 

Nickel-Catalyzed Coupling of Aryl O-Carbamates with Grignard Reagents, Synthesis of 2,7-Dimethylnaphthalene and Derivatives. 

NICKEL-CATALYZED COUPLING OF ARYL O-CARBAMATES WITH GRIGNARD REAGENTS 2,7-DIMETHYLNAPHTHALENE... 

In the area of organometallic chemistry, we begin with a procedure for the palladium-catalyzed animation of aryl halides and aryl triflates, illustrated by syntheses of N-HEXYL-2-METHYL-4-METHOXYANIUNE and N-METHYL-N-<4-CHLOROPHENYL)-ANILINE. The next procedure describes the synthesis of 1,2,3,4-TETRAHYDROCARBAZOLE by the palladium-catalyzed annulation of ketones with o-iodoaniline. Next, a procedure for the synthesis of 2,7-DIMETHYLNAPHTHALENE via the nickel-catalyzed coupling of aryl O-carbamates with Grignard reagents is presented. The fourth procedure in this section describes the synthesis of 5-METHYL-2,2 -BIPYRIDINE by a Negishi cross-coupling reaction... 

R Nickel-Catalyzed Coupling of Aryl 0-Carbamates with Grignard... 

Scheme 30. Nickel-catalyzed cross-coupling of O-aryl carbamates and triflates with Grignards electronic and steric effects.

Scheme 31. Nickel-catalyzed O-aryl carbamate Crignard cross-coupling regiospecific access to 1,2,3- and 2,3-substituted naphthalenes.

For the synthesis of the non-diene analogue 65, which bears a benzyl group in the terminal position (Scheme 17), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) cleavage of the p-methoxybenzyl (PMB) ether at the C15-position did not proceed in the presence of the benzyl moiety (oxidation of the methylene in allylic-benzylic-position in C23-position). Therefore, we inverted the order of the first two steps (1) DDQ deprotection on 44 and (2) nickel-catalyzed cross-coupling reaction performed on a free primary alcohol in C15 position. After this minor modification, completion of the synthesis followed the established route Suzuki-Miyaura crosscoupling reaction between alkyl iodide 73 (via its trialkylboronate species) and vinyl iodide 60 to yield 74 selective carbamate installation and final deprotection to afford DDM analogue 65. 

Utilizing similar conditions as Ackermann. Ackermann [153] also showed the C-H arylation of azine N-oxides with aryl tosylates and mesylates with their own protocol (but changed the base from K2CO3 to CsF). Very recently, Itami [154] discovered the first nickel-catalyzed C-H/C-O coupling between 1,3-azoles and various phenol derivatives such as aryl pivalates, carbamates, sulfamates, mesylates, and tosylates. Surprisingly, these reactions only proceeded when 1,2-bis(dicydohexylphosphino)ethane (108 dcype) was used as Hgand (Scheme 17.30). 

Itami s group developed a nickel-catalyzed cross-coupling of aryl pivalates, carbamates, and carbonates with azoles [Eq. (14)] [63]. The use of bidentate 1,2-bis(dicyclohexylphosphino)ethane is essential for the reaction to proceed. 

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