Trideep Rajale

Multicomponent reactions for the synthesis of heterocycles.

Multicomponent domino reactions (MDRs) serve as a rapid and efficient tool for the synthesis of versatile heterocycles, particularly those containing structural diversity and complexity, by a one-pot operation. These reactions can dramatically reduce the generation of chemical wastes, costs of starting materials, and the use of energy and manpower. Moreover, the reaction period can be substantially shortened. This Review covers recent advances on multicomponent domino reactions for the construction of five-, six-, and seven-membered heterocyclic skeletons and their multicyclic derivatives.

Asymmetric catalytic Strecker reaction of N-phosphonyl imines with Et2AlCN using amino alcohols and BINOLs as catalysts

The asymmetric catalytic Strecker reaction of achiral N-phosphonyl imines with Et(2)AlCN has been established. Both free amino alcohols and BINOLs have been proven to be effective catalysts to afford excellent enantioselectivities and yields. The N-phosphonyl group can be readily cleaved under mild conditions and enable purification of crude products by simple washing with hexane. The cleaved N,N-dialkyl diamine auxiliary can be recovered quantitatively via n-BuOH extraction. The scope for both N-phosphonyl imines and catalysts was vastly studied for this new catalytic system.

Asymmetric hydrophosphylation of chiral N-phosphonyl imines provides an efficient approach to chiral α-amino phosphonates.

Chiral N‐phosphonylimines were found to react with lithium phosphites to provide various substituted chiral α‐amino phosphonates in excellent yields (94–97%) and diastereoselectivities (93:7–99:1). The types of bases utilized for generating the nucleophile are crucial for the effectiveness of asymmetric induction. In addition, N,N‐isopropyl group on chiral N‐phosphonylimine auxilliary was proven to be superior to other protecting groups in controlling diastereoselectivity. The absolute configuration was unambiguously determined by converting a chiral α‐amino phosphonate into its authentic N‐Cbz derivative.

Competitive Pseudopericyclic [3,3]- and [3,5]-Sigmatropic Rearrangements of Trichloroacetimidates

The Woodward-Hoffmann rules predict whether concerted pericyclic reactions are allowed or forbidden based on the number of electrons involved and whether the cyclic orbital overlap involves suprafacial or antarafacial orbital overlap. Pseudopericyclic reactions constitute a third class of reactions in which orthogonal orbitals make them orbital symmetry allowed, regardless of the number of electrons involved in the reaction. Based on the recent report of eight-centered ester rearrangements, it is predicted that the isoelectronic eight-centered rearrangements of imidates would also be allowed. We now report that these rearrangements occur, and indeed, an eight-centered rearrangement is slightly favored in at least one case over the well-known six-centered Overman rearrangements, in a trichloroacetimidoylcyclohexadienone, a molecular system where both rearrangements are possible.

Research Article: Asymmetric Hydrophosphylation of Chiral N-Phosphonyl Imines Provides an Efficient Approach to Chiral α-Amino Phosphonates

Chiral N‐phosphonylimines were found to react with lithium phosphites to provide various substituted chiral α‐amino phosphonates in excellent yields (94–97%) and diastereoselectivities (93:7–99:1). The types of bases utilized for generating the nucleophile are crucial for the effectiveness of asymmetric induction. In addition, N,N‐isopropyl group on chiral N‐phosphonylimine auxilliary was proven to be superior to other protecting groups in controlling diastereoselectivity. The absolute configuration was unambiguously determined by converting a chiral α‐amino phosphonate into its authentic N‐Cbz derivative.

Research Article: Asymmetric Hydrophosphylation of Chiral N-Phosphonyl Imines Provides an Efficient Approach to Chiral α-Amino Phosphonates: Asymmetric Hydrophosphylation of Chiral N-Phosphonyl Imines

Chiral N‐phosphonylimines were found to react with lithium phosphites to provide various substituted chiral α‐amino phosphonates in excellent yields (94–97%) and diastereoselectivities (93:7–99:1). The types of bases utilized for generating the nucleophile are crucial for the effectiveness of asymmetric induction. In addition, N,N‐isopropyl group on chiral N‐phosphonylimine auxilliary was proven to be superior to other protecting groups in controlling diastereoselectivity. The absolute configuration was unambiguously determined by converting a chiral α‐amino phosphonate into its authentic N‐Cbz derivative.