Novel route to carboxylic acids via the DCME reaction

B-Alkyl sp3-sp2 Suzuki-Miyaura Couplings under Mild Aqueous Micellar Conditions

Use of B-sp³-alkyl reagents for Suzuki-Miyaura couplings under aqueous micellar catalysis conditions is reported. Studies as to substrate scope, use in a four-step one-pot sequence, and reaction medium recycling exemplify the synthetic utility of this technology. OBBD ( B-alkyl-9-oxa-10-borabicyclo[3.3.2]decane) derivatives are easily made and utilized for couplings under mild conditions. Comparisons were also made between OBBD and 9-BBN ( B-alkyl-9-borabicyclo[3.3.1]nonane) derivatives as reaction partners.

Chelation-assisted substrate-controlled asymmetric lithiation-allylboration of chiral carbamate 1,2,4-butanetriol acetonide

The lithiation of 2-(2,2-dimethyl-1,3-dioxolan-4-yl)ethyl diisopropylcarbamate (1) is achieved freely by sec-butyllithium in diethylether with high lk-diastereoselectivity: the bicyclic chelate complexes 3a and 3b are reacted with electrophiles to form optically active precursors 4a and 4b with >95% diastereoselectivity. In addition, tertiary diamines can undergo an external complexation in contest with the internal oxygen ligand, leading to improved stereoselectivities. The further reactions of lithiated carbamates with trans alkenyl-9-BBN derivatives after 1,2 metallate rearrangements, gave the key intermediate α-substituted allylic boranes 7. Subsequent allylboration of aldehydes gave (Z)-anti-homoallylic alcohols 8 in good yield and excellent d.r.

(E)-2-boryl-1,3-butadiene derivatives of the 10-TMS-9-BBDs: highly selective reagents for the asymmetric synthesis of anti-1,2-disubstituted 3,4-pentadien-1-ols

The efficient stepwise construction of optically pure trans-4-substituted 2-boryl-1,3-butadienes 6 is described. Hydroboration of 1-alkynes with either enantiomeric form of 3 leads to the pure trans-1-alkenylboranes 4 which undergo addition of alpha-ethoxyvinyllithium followed by a BF(3)-mediated 1,2-B-->C vinylic group migration to provide 6. These organoboranes 6 serve as a new type of asymmetric allylborating agent providing an extremely selective protocol for the preparation of anti-1,2-disubstituted 3,4-pentadien-1-ols 8 as essentially single diastereomers in enantiomerically pure form. One example of a cis-2-boryl-1,3-butadiene (9) was prepared through a Grignard procedure. It was found to provide the corresponding syn-alcohol 11. The utility of 8 was demonstrated in their conversion to substituted beta-hydroxy acids 12 through ozonolysis and to substituted alpha,beta-unsaturated-delta-lactones 13 through Ru-catalyzed cyclocarbonylation.