Is it possible to make N-way Controlled-NOTs out of Toffoli gates, without extra work bits?
It's not possible.

A reversible computation always corresponds to a permutation of the state space. When working on three bits, a Toffoli corresponds to a single swap in the state space (it swaps 111 for 110). When working on four or more bits, a Toffoli gate always corresponds to an even number of swaps in the state space. This is because it performs a swap for each possible state of the uninvolved bits, and there are an even number of such states. For example, a Toffoli applied to the first three bits of a four bit system swaps 111_0 for 110_0 and swaps 111_1 for 110_1. Even number of swaps.

Permutations have a parity. A permutation that can be implemented with an even number of swaps has even parity. Permutations that can be implemented with an odd number of swaps have odd parity. The composition of two even parity permutations will also be an even parity permutation. Odd parity permutations can't be reached by composing even parity permutations.

This means the Toffoli gate can't perform a CCCNOT without workspace, because the action of the CCCNOT on the state space is an odd parity permutation but the action of the Toffoli is an even parity permutation. The single CNOT and NOT gates have the same problem. You need an extra work bit (or quantum gates like $X^{1/8}$) to break the parity barrier.