Addition and Cycloaddition Reactions of Phosphinyl- and Phosphonyl-2H-Azirines, Nitrosoalkenes and Azoalkenes

Abstract

An overview of the use of 2H-azirines, conjugated nitrosoalkenes and conjugated azoalkenes bearing phosphorus substituents in addition and cycloaddition reactions is presented, focused on strategies for the synthesis of aminophosphonate and aminophosphine oxide derivatives.

Construction of bis-, tris- and tetrahydrazones by addition of azoalkenes to amines and ammonia

“…After brief optimization of the reaction conditions (solvent, base and ratio of reagents), it was found that alkylation of benzylamine with 2.0 equiv of Boc-hydrazone 1a and 2.0 equiv of potassium carbonate as a base in MeOH led to bishydrazone 2a in highest yield. The bright yellow color appeared in course of reagents mixing indicating the formation of azoalkene intermediate A [35–39]. Under these conditions, a range of other α-halogen hydrazones 1b–d , f , g were successfully converted to corresponding bishydrazones 2b–d , f , g in good to high yields (Table 1).…”

“…In the present work, we focused on the development of a general approach to tertiary amines and polyamines bearing several hydrazonomethyl arms at the nitrogen atom(s). To achieve this goal, we suggested a straightforward methodology based on multiple Michael-type additions of azoalkenes A (generated from α-halogen azacarbonyl precursor 1 [35–39]) to amines or ammonia (Scheme 1). …”

“…Though the chemistry and synthetic potential azoalkenes A have been a subject of considerable interest in the recent years [38–39], their reactivity with amines is poorly explored. It has been demonstrated that amines react with azoalkenes A forming α-aminohydrazones (Scheme 1) [35–49], however, addition of several azoalkene molecules to amines is virtually unknown.…”

Hetero-Diels-Alder Reactions of In Situ-Generated Azoalkenes with Thioketones; Experimental and Theoretical Studies

“…Azoalkenes (1,2-diaza-1,3-dienes) 4 ( Scheme 2 ) are structurally and electronically related to 1-oxa-2-aza-1,3-dienes 2 ( Scheme 2 ) and currently attract great attention as versatile substrates for hetero -Diels-Alder reactions performed with various dienophiles. The importance of this research is reflected by a large number of excellent review articles, which appeared in the last two decades [ 23 , 24 , 25 , 26 , 27 ]. Numerous original publications appear regularly.…”

Regioselectivity in Hetero Diels–Alder Reactions

“…The past several decades confirmed conjugated azoalkenes (also called 1,2-diaza-1,3-dienes or DDs; e.g., Scheme , heterodienes 2 or 5 ), mostly obtained via dehydrohalogenation of the respective α-halo-hydrazones 1 or 4 (Scheme ), as powerful intermediates in the synthesis of an impressive number of new heterocyclic systems either through hetero Diels–Alder cycloaddition or 1,4-conjugate addition reactions. Examples of these reactions are shown in Scheme . , …”