A Sakurai-Prins-Ritter sequence for the three-component diastereoselective synthesis of 4-amino tetrahydropyrans.

A simple one-pot procedure for the Sakurai-Prins-Ritter sequence allows rapid assembly of 4-acylamino-2,6-substituted tetrahydropyrans in high yields and with excellent diastereoselectivity from readily available 4-acetoxy-1,3-dioxanes, allylsilanes, and nitriles. A variety of nitriles have been shown to participate. Diastereoselectivities are uniformly high and observed stereochemistry of cation trapping proceeds according to Alder's model of the 4-tetrahydropyranyl cation.

Diastereoselective, titanium-mediated cyclization of omega-vinyl tethered imides.

[reaction: see text] Diastereoselective reductive coupling reactions of omega-vinyl tethered cyclic imides are achieved by a preexisting stereocenter at an allylic position. Particularly noteworthy is the effective use of a 1:2 mixture of Ti(O-i-Pr)4 and n-BuLi to afford the N-acylhemiaminal products in good yields.

Titanium-mediated alkylative coupling of N-acylpyrroles.

[reaction: see text]. Inter- and intramolecular titanium-mediated coupling reactions of N-acylpyrroles are reported for convenient functionalization of terminal olefins. Comparison with the Kulinkovich reaction of esters and other carboxylic acid derivatives is also included.