A new transition-metal-free amination of pyridine-2-sulfonyl chloride and related N-heterocycles using magnesium amides of type RNMgCl·LiCl is reported. Additionally, the directed ortho-magnesiation of pyridine-2-sulfonamides using TMPMgCl·LiCl was investigated. Reaction of the magnesium intermediates with various electrophiles and subsequent amination using magnesium amides led to a range of 2,3-functionalized pyridines. Also, cyclization reactions providing an aza-indole and an aza-carbazole were carried out.

Functionalized 4-benzylated pyridines can be efficiently prepared by a transition-metal-free cross-coupling between various benzylic zinc chlorides and substituted 4-cyanopyridines in THF/DMPU under microwave irradiation (40 °C, 0.5-1.5 h). Selective benzylations on polycyano-aromatics have also been achieved under these mild conditions. We also report a novel oxidative nucleophilic substitution of a hydrogen on 1,3-dicyanobenzene using benzylic zinc reagents.

The zincation of various 1-(trimethylsilyl)-3-aryl-1-propynes with TMPZnCl·LiCl followed by a Pd-catalyzed coupling with aryl halides provides arylated allenes in 52-92% yield. Subsequent metalation with TMPZnCl·LiCl and cross-coupling with a second different aryl halide provides regioselectively tetrasubstituted allenes in 42-70% yield. This sequence can be performed in a one-pot procedure. DFT calculations and NMR studies support the formation of allenylzinc and propargyllithium intermediates starting from 1-(trimethylsilyl)-3-phenyl-1-propyne.

A set of functionalized alkynylpyridines can be readily obtained using Et 2 O·BF 3 as promoter. Alkynyllithium reagents undergo an addition reaction at position C-2 of pyridines that are rearomatized by oxidative treatment with chloranil. These substituted pyridines can be easily converted into more valuable intermediates. Examples of applications are given as well. Finally, the synthesis of piperidines and lactams via first an oxidative BF 3 -mediated addition reaction followed by a NaBH 4 reduction or acidic workup is also described.

Reactions of the new, conveniently prepared benzylic manganese reagents with aldehydes (II), acid chlorides (V), aryl bromides (VII) as well as nitrostyrene (IX) proceed without any additional transition metal. -(QUINIO, P.; BENISCHKE, A. D.; MOYEUX, A.; CAHIEZ, G.; KNOCHEL*, P.; Synlett 26 (2015) 4, 514-518, http://dx.

Functionalized benzylic manganese chlorides were smoothly prepared by the direct insertion of magnesium into benzylic chlorides in the presence of MnCl 2 ·2LiCl. Reactions with acid chlorides, aldehydes, an allyl bromide, and an enone proceed without any additional transition metal.

The addition of bromomagnesium 2-vinyloxy ethoxide to various aldehydes in the presence of 10 mol% Sc(OTf) 3 provides a broad range of functionalized protected aldol compounds. The enantioselective preparation of these aldols can be achieved via a Swern oxidation-CBS reduction sequence. Use of the dioxolane derived from 2-bromocyclohexanone provides the expected aldol product as the anti diastereoisomer (dr >99:1).

A coupling reaction of benzylic zinc chlorides and 4‐pyridinenitriles under microwave irradiation gives 4‐benzylpyridines efficiently.