Allyl alcohols were converted to allyl boronic acids and subsequently to trifluoro(allyl)borates with tetrahydroxy diboron using palladium pincer-complex catalysis. These reactions are regio- and stereoselective proceeding with high isolated yields. Competitive boronation experiments indicate that under the applied reaction conditions the allylic displacement of a hydroxy group is faster than the displacement of an acetate leaving group. It is assumed that the hydroxy group of the allyl alcohol is converted to a diboronic acid ester functionality, which can easily be substituted.

An efficient one-pot procedure was designed by integration of the pincer-complex-catalyzed borylation of allyl alcohols in the Petasis borono-Mannich reaction and in allylation of aldehydes and ketones. These procedures are suitable for one-pot synthesis of alpha-amino acids and homoallyl alcohols from easily available allyl alcohol, amine, aldehyde, or ketone substrates. In the presented transformations, the active allylating agents are in situ generated allyl boronic acid derivatives. These transient intermediates are proved to be reasonably acid-, base-, alcohol-, water-, and air-stable species, which allows a high level of compatibility with the reaction conditions of the allylation of various aldehyde/ketone and imine electrophiles. The boronate source of the reaction is diboronic acid or in situ hydrolyzed diboronate ester ensuring that the waste product of the reaction is nontoxic boric acid. The regio- and stereoselectivity of the reaction is excellent, as almost all products form as single regio- and stereoisomers. The described procedure is suitable to create quaternary carbon centers in branched allylic products without formation of the corresponding linear allylic isomers. Furthermore, products comprising three stereocenters were formed as single products without formation of other diastereomers. Because of the highly disciplined consecutive processes, up to four-step, four-component transformations could be performed selectively as a one-pot sequence. For example, stereodefined pyroglutamic acid could be prepared from a simple allyl alcohol, a commercially available amine, and glyoxylic acid in a one-step procedure. The presented method also grants an easy access to stereodefined 1,7-dienes that are useful substrates for Grubbs ring-closing metathesis.

Palladium-catalyzed boronation of vinyl cyclopropane, vinyl aziridine, and allyl acetate substrates could be accomplished using tetrahydroxydiboron reagent in the presence of SeCSe pincer complex catalyst 1a. These reactions result in allyl boronic acids, which were converted to synthetically useful trifluoro(allyl)borates or allyl boronates. The catalytic transformations proceed under mild and neutral conditions, and therefore many functionalities Br, COOEt, ArSO2(NH), OAc, and SiRMe2 are tolerated. The selectivity of the presented processes is very high, affording the linear products incorporating a trans double bond.

Palladium-catalyzed coupling reactions of functionalized allylboronic acids with iodobenzenes were achieved under standard Suzuki-Miyaura coupling conditions. The coupling reactions afforded selectively the branched allylic products in high to excellent yields. In contrast to palladium-catalyzed nucleophilic substitution reactions proceeding via (eta3-allyl)palladium intermediates, this process does not require directing groups in the allyl moiety to achieve substitution at the congested allylic terminus. The regioselectivity of the process was largely unaffected by the substituent effects of the iodobenzenes and the allylic substrates.

The highly regio-and stereoselective coupling of allyl alcohols with aldehydes could be achieved with 5 mol-% of SeCSe pincer complex catalyst and p-toluenesulfonic acid in the presence of diboronic acid. The transformations have a broad synthetic scope, and the high yields were obtained Catalytic allylation of the carbonyl carbon of aldehydes with allyl alcohols is one of the most attractive transformations in palladium chemistry. [1,2a-2d] In practical implementations, the allylation reaction is initiated by a palladiumcatalyzed conversion of allyl alcohols to allylmetal species. This conversion is mediated by SnCl 2 ,[2a] BEt 3 , [2b] Et 2 Zn [2c] and indium [2d] salts (Scheme 1). Subsequently, the allylmetal species undergoes electrophilic allylation with the aldehyde substrate.[2e-2g] As these transformations involve a two-step procedure with a Lewis acid and/or reductive organometallic reagent, the functional group tolerance of the reaction is usually limited. With the use of functionalized allyl alcohols, a further issue is the control of the stereoselectivity of the process, which is highly dependent on the applied organometallic reagent and on the steric bulk of the allylic substituent. Although there are many excellent procedures described in the literature, [1,2a-2d] it is still a challenge to find highly selective and robust methods for the palladium-catalyzed coupling of various allyl alcohols (including both cyclic and acyclic ones) with aliphatic and aromatic aldehydes. We have now found that allyl alcohols 1a-g react readily with aldehydes 2a-i in the presence of diboronic acid (3), catalytic amounts (5 mol-%) of easily accessible pincer com-